Acta Path. Jap. 29(3): 363-375, 1979
PRIMARY MALIGNANT PERIPHERAL NERVE TUMORS (MALIGNANT SCHWANNOMAS) A Clinicopathologic and Electron Microscopic Study Masazumi TSUNEYOSRI and Munetomo ENJOJI The Becond Department of Pathology, Faculty of Medicine, Kywhu University (Received on Aug. 18, 1978)
A clinicopathologic and electron microscopic study was performed on 35 cases of primary malignant peripheral nerve tumors, among which 12 developed in association with neurofibromatosis (von Recklinghausen's disease) and further 11 in keeping with anatomically discernible nerves in patients without neurofibromatosis. Depending upon the histologically predominant pattern, these tumors were subdivided into three groups: 23 compact spindle cell, 6 myxoid, and 6 epithelioid varieties of the tumor. The common ultrastructures in three of the 35 tumors were as follows: 1) The cell membranes manifested characteristic infoldings and lamellar configuration. 2) The tumor cell surfaces were coated by occasional basal lamina or homogeneously electrondense membranous material. 3) The cytoplasms contained well-developed organelles and a few neurosecretory-type granules. Differential points from other soft-tissue sarcomas were briefly discussed on the histologic basis. ACTA PATH. JAP. 29: 363-375, 1979.
Introduction
Primary malignant tumors of peripheral nerves are comparatively rare but exhibit a variety of clinical and histologic appearances. Since the epochal work of STEWART and COPELANDin 1931,1a there has been much discussion about the clinicopathologic features and biologic behavior of the tumors.3~8~10~17~2a~23 The whole scope of the tumors, however, is not as yet defined. The present authors, therefore, undertook a clinicopathologic review of 35 lesions interpreted as malignant peripheral nerve tumors. Of the 36 tumors, 12 developed in association with neurofibromatosis (von Recklinghausen's disease) including seven cases with anatomical localization of the tumor in peripheral nerves, and 11 other tumors were related anatomically to discernible nerves in patients without neurofibromatosis. Three of the 36 tumors were studied electron microscopically by contrasting the fine structures in a normal peripheral nerve, three neurilemomas and four neurofibromas. E27 iEB, B%Z? R h Supported by Grants-in-aid for Cancer Research 1976 and 1977 from the Ministry of Health and Welfare and 1977 from Ministry of Education, Science and Culture of Japan and by Grant from the Fukuoka-ken Anti-Cancer Association, 1976. Mailing address: Dr. M. ENJOJI,Second Department of Pathology, Faculty of Medicine, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812, Japan. 363
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Materiak and Methods The source of materials for this study is about 7,000 cases of soft-tissue tumors in the files of the Second Department of Pathology, Faculty of Medicine, Kyushu University. The registry now covers the period 1956-1976,end there were 36 cases of malignant tumors of peripheral nerves. Of the 35 tumors, 23 developed in association with von Recklinghausen’s disease or involved anatomically discernible nerve& Furthermore, 12 additional cases, though lacking such association as mentioned above, were selected because the tumor exhibited the microscopic features which convinced us of nerve origin and malignant nature, closely resembling the features in the foregoing cases. All of the paraffi blocks available were recut and stained with hematoxylin and eosin. Special stains employed when necesaary included Masson’s trichrome stain, silver impregnation for reticulin, alcian blue and PAS stains, Bodian’s nerve fiber, stain, Sevier-Munger neural tissue stain, Fontana stain for melanin, and Grimelius stain for argyrophil granules. Fresh tissues for electron microscopy were available in three cases of the malignant peripheral nerve tumor. The tissues were fixed in 3% glutctraldehyde solution (buffered pH 7.4) end were postfixed in 1% phosphate-buffered osmium tetroxide. Following dehydration the tissue blocks were embedded in Epon 812 and were cut on an LKB ultrotome 111. The sections were stained with urenyl acetate and lead citrate. The electron microscope used was a JEM 100 C. I n addition, frmh tissues from a normal ulnar nerve, three neurilemomasand four neurofibromas were prepared by the same method for comparative electron microscopy.
Clinical Features Sea: and Age Of the 35 patients, 11 were males and 24 were females. The age of the patients ranged from 11 to 86 years with the mean of 40 years (Fig. 1).
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Anatomical Site The tumors were attached anatomically to peripheral nerves in 18 of the 36 cases. Eleven tumors (31%) were located in the lower extremities, 10 (29%) in the upper extremities, 7 (20%) in the trunk, 3 in the retroperitoneum, 2 in the head and neck region and 2 in other sites (Fig. 2). There is none of multiple primary tumors.
C l i n h l History A swelling or lumpy mass was almost always the chief sign to attract the patient’s attention. In 21 of the 35 patients, the masses were associated with pain. Of the 35, 12 (34%) had developed in association with neurofibromatosis (von Recklinghausen’s disease), including seven cases with a tumor closely connected anatomically to grossly discernible peripheral nerves. Of the 23 cases unassociated with neurofibromatosis, 11 had a close anatomical relation to discernible nerves. Fig. 1. Frequency in various decades and sexes.
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Fig. 2. Anatomical distribution.
Pathology Macroscop.ic Observations The size of tumors a t the time of the first excision varied from a small-finger’s tip to a child’s head. Grossly, the tumor was well circumscribed in 22 patients (73%) and showed infiltrating growth in 13 (27%). The consistency was usually described as elastic soft. The cut-surface was either parenchymatous or myxomatous with gray-white to gray-yellow color (Fig. 3).
Light Mioroscopic Pindings Histologic features showed a considerable variety. The tumors were usually composed predominantly of plump, spindle, mononuclear cells admixed with a small number of round and polygonal cells. These cells were packed in interlacing or fascicular bundles, showing
Fig. 3. Typical gross appearance consisting of a multilobulated graywhite tumor within the ulnar nerve of a 51-year-old woman.
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complicated loose and dense arrangements or sometimes a “herring-bone” pattern. Occasionally, the tumors had a myxoid matrix, or an undulating or a perithelial pattern of tumor cells. Not infrequently in others or in different portions of the same growth, there were peculiar and distinct alignments of tumor cells in epithelioid structures. Nuclear palisading appeared clearly in six cases (Fig. 4). Gland-like s t r u ~ t u r e s ~ , ~ ~ , 2 5 lined by columnar or cuboidal cells were identified in two cases. In eight cases (23%), there existed a neurofibroma-like pattern in some portions of the tumor (Fig. 6). The tumor cells were spindle, polygonal or round in shape and usually showed certain uniformity. Only occasionally, however, there were foci of pleomorphism of tumor cells, and in seven cases (20%) giant cells of mononucleate and multinucleate types were sparingly distributed throughout the neoplastic tissue. The number of mitoses averaged three with a range from zero to 10 per each high-power field. Small calcium deposits were identified in two tumors. There were also occasional areas of hemorrhage and necrosis in the tumors. Although there was such a variation as mentioned above in histologic appearance in the malignant peripheral nerve tumors, the tumors could be divided reasonably into the following three groups depending upon the predominant or most striking pattern of each tumor: 1) compact spindle cell group, 2) myxoid group and 3) epithelioid group (Table 1). Table 1. Histological Claaa$cation
No. pt.
% Pt.
23
66
3. Epithelioid group
6 6
17 17
Total
36
100
Histological type 1. Compact spindle cell group 2. Myxoid group
Compact Spindle Cell Group (23 m e s ) The tumors in this group were composed of plump or slender spindle cells (Fig. 6). The cells were compactly arranged in bundles that produced interlacing fascicles, often exhibiting palisading, herring-bone or some other particular patterns, The tumor cells showed a fair uniformity. They had faintly acidophilic, scanty or moderately abundant cytoplasm possessing delicate fibrillary processes. The nuclei of the tumor cells were commonly of an oval or more elongated shape with smooth surfaces and rather thin nuclear membranes. The nuclear chromatin was diffusely stippled. Some of the tumors in this group were composed predominantly slender spindle cells with collagen production and were reminiscent of fibrosarcoma. In rare instances, the characteristic feature was perivascular growth of tumor cells with proliferation of vascular endothelial cells. I n one case, there were tophus-like depositions of hyaline, showing radial arrays of tumor cells (Fig. 7).
Myxoid Group (6 cases) The tumor cells were gathered in complicated loose and dense areas. The feature of the dense areas is essentially similar to those of the
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Fig. 4. Nuclear palisading identified in the tumor of the same case as Fig. 3.H & E, x 110. Fig. 5. Neurofibroma-like pattern identified in some area of an epithelioid type tumor. H & E, x 91. Fig. 6. Compact spindle cell type arising in the tibia1 nerve with von Recklinghausen’s disease. The tumor cells are compactly arranged in fascicles (H & E, x 180). The inset shows the presence of wavy and delicate hair-like fibrils about the tumor cells. Silver impregnation for reticulin, x 450. Fig. 7. Tophus-like depositions of hyaline showing radial arrays of tumor cells identified in the tumor of a 21-year-old woman. H & E, 136.
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Fig. 8. Myxoid type arising in the sciatic nerve. The tumor cells reveal complicated loose and dense arrangement. Predominant myxoid areas consisting of pools hyaluronidase-sensitive acid mucopolysaccharide is a common finding. H t E, x 90. Fig. 9. Epithelioid type arising in the iilnar nerve with von Recklinghausen’s disease. Epithelial cell-like cells are arranged in small solid nests. H t E,
x 105. Fig. 10. Glandular variant of epithelioid type in the sciatic nerve with von Recklinghausen’s disease. Predominant areas consist of epithelioid arrangement with scattering atypical gland-like structures. H BE E, x 350.
compact spindle cell group. In the loose areas, however, the spindle tumor cells were loosely arranged in interlacing or streaming, sometimes undulating fascicles or in reticular networks, and were separated individually by a myxoid matrix (Fig. 8). The perithelial arrangement of atypical round or spindle cells with plump nuclei was sometimes prominent. The myxoid matrix were stained for acid mucopolysaccharides with
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alcian blue. A neurofibroma-like pattern was often a counterpart of this type and was identified at least in some portions of the tumor. The tumor cells were bipolar spindle cells or stellate cells with anastomosing plasmatic processes which tended to form a syncytial network. The cytoplasm was fibrillary and brightly acidophilic. There were occasional giant cells of mononucleate and multinucleate types. These cells had delicate fibrillary cytoplasmic processes, and had neither lipid droplets nor cross striations in their cytoplasm. Epithelioid group (6 cases) All the tumors of this group arose in anatomically discernible nerves or in somatic soft tissue in association with neurofibromatosis. In areas of epithelioid structures, the tumor cells were round, polygonal, plump or spindle and were arranged in solid nests, clusters or whorls (Fig. 9). The tumor cells were often intimately related to thin vascular channels. Some had abundant cytoplasm that was either pale or eosinophilic and homogeneous. The tumor cells frequently contained large nuclei with prominent nucleoli. The cell type and the arrangement simulated the appearance of nonpigmented areas of a malignant melanoma. One case, which could be classified as another rare type “glandular type”, showed unique foci of glandular differentiation, cellular portion of the tumor containing atypical gland-like structures lined by epithelial-like pseudostratified columnar or nonciliated cuboidal cells (Fig. 10). Histochemical Findings
Silver impregnation for reticulin or Bodian’s nerve fiber stain revealed the presence of wavy and delicate hair-like fibrils which entwined in a sleeve-like or straightwire fashion about tumor cells (Fig. 6). Alcian blue positive material was identified among the loosely arranged tumor cells. Neither PAS-positive material nor lipiddroplets were identified in the cytoplasm of the tumor cells. There was no Grimelimpositive granules in tumor cells either. Electron Microscopic Findings (3 Cases)
The tumor cells were polygonal mononucleated cells or plump spindle cells. The cell membranes were of indefinite morphology. Some cells exhibited characteristic whorl-like or lamellar structures resembling Schwann cells of Antoni type A neurilemoma t i s s ~ (Figs. e ~ ~ 11 ~ and ~ 12), while others had pseudopodia-like, finger-like or bubblelike structures resembling those of Antoni type B neurilemoma tissue or of neurofibroma 20~24(Fig. 13). Prominent myelin figures and pinocytotic vesicles were identified in the cell membranes in one case (Fig. 12a). The tumor cells were partly surrounded by basement membrane or homogeneous electron dense membranous material in three cases (Figs. 12b and 13). The nuclei of the tumor cells were round or ovoid in shape, smooth in outline with occasional invaginations in their membranes. Chromatin was of an even distribution. Nuclei-cytoplasmic ratio of tumor cells was high as shown in light microscopy. Among cytoplasmic organelles, large aggregates of small vesicles and free ribosomes were frequently observed together with scattered mito-
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Fig. 13. Electron micrograph of a case arising in the brachial nerve. Right: Irregular infoldings of the cytoplasmic processes with occasional lamina of basement membranous material. x 9,600. Upper left: A portion of tumor cell surrounded by the basal lamina. x 42,500. Lower left: Light micrograph of the same case. H &, E x 440.
chondria, Golgi apparatus, endoplasmic reticulums and intracytoplasmic microfibrils. In two cases of compact spindle cell type, a characteristic feature was the presence of intracytoplasmic cored vesicles (neurosecretory-type granules) measuring 100 to 260 mp in diameter. In one such case focal aggregations of intracytoplasmic cored vesicles were observed (Fig. 14), while in the other case a very small number of cored vesicles was identified in tiny areas. Extracellular space contained a wide assortment of structural components, including numerous bundles of collagen, microfibrils and amorphous material. Treatment and Prognosis
There was tumor recurrence in 24 (68%) of the 35 patients. Twenty-two of the 28 instances treated solely by simple excision recurred, the first recurrence occurring within 1.5 years in nearly all patients. Metastases were identified in 10 (29%) of the 35 cases. The commonest site of metastasis was the lung. Fig. 11. Electron micrograph of a compact spindle cell type showing nuclear palisading seen in Fig. 4. The cell membranes show characteristic lamellar infoldings. x 9,140. Fig. 12. High magnification of Fig. 11. Pinocytotic vesicles (a), and lamina of bmement membranous material (b)are prominent. Fig. 8. x 67,600; Fig. b, x 32,500.
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Fig. 14. Electron micrograph of a cellular area of the same case as Fig. 4. Several dense core secretory granules (arrow) are found in the clear cytoplasms. x 4,670. The inset is a high magnification of the cytoplasmic granules measuring 100 to 200 mp in diameter. x 41,400.
All 35 patients had been treated surgically, the operation being radical in four patients. Of the 29 patients in whom follow-up information was obtained, 15 died of tumor between 4 months and 5 years after initial treatment and 14 patients are surviving. Out of the 14 survivors, five are living for more than five years. The five-year survival rate of all cases was 30%. In the compact spindle cell group, seven of the 23 patients have died and eleven are surviving. In the myxoid group, four of the six have died and one surviving for three years. In the epithelioid group, four of the six have died and two surviving. Out of the 12 patients having neurofibromatosis, three were living and well and seven died of the disease at the end of the follow-up period. DiScuSsiolz
Primary malignant tumors of peripheral nerve had relatively variable clinical and morphologic features. Nevertheless, since early-day review of malignant peripheral nerve tumors by STEWARTand COPELAND(1931)l”there have as yet been no conclusive results for their clinicopathologic features and biological behavior of the tumors. According to the WHO histological classification of soft-tissue tumors in 196g4, the term “malignant tumors of peripheral nerves” specifies the following categories: 1)
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malignant schwannoma (neurogenic sarcoma, neurofibrosarcoma), and 2) peripheral tumors of primitive neuroectoderm. The tumors the present authors were dealing with in this study were in reality malignant schwannomas. They have divided the tumors into the following three groups with descriptive terms on a histologic basis (Table I ) : 1) compact spindle cell, 2) myxoid, and 3) epithelioid. In this series, the compact spindle cell type occurred most commonly and in 23 cases (66%). The myoxid type bearing a superfkial resemblance to myxoid liposarcoma or myxoid malignant fibrous histiocytoma appeared in 6 cases (17%). The epithelioid type occurred in 6 cases (17%)4. Some tumors of this type were reminiscent of malignant melanoma because of their epithelioid character, though failing to show melanin pigment?JO,lS One of the cases showed unique foci of atypical gland-like structures lined by epithelial-like pseudostratified nonciliated cells, the features being consistent with those in “glandular schwannoma” reported by WOOD RUFF.^^ Under electron microscopy the tumor cells, despite of the variation in differentiation, often showed fundamental characteristics of Schwann cells. It was noteworthy that very characteristic features of the tumor cells consisted in the formation of cytoplasmic processes and in the structure of their cell membranes.6,20 The cell membranes exhibited characteristic infoldings and lamellar configuration. In particular, one case of the compact spindle cell type showing a histological pattern of nuclear palisading was characterized ultrastructurally by prominently lamellar or whorl-like infoldings of cell membranes which resembled those of Schwann cells in Antoni type A neurilemoma tissue. 6~w),24 Occasional myelin formation in cell membranes was identified. The presence of basal lamina or homogeneously electron dense membranous material which coated the exposed cell surface, was another major factor in excluding identification from a fibroblast. The intracytoplasmic organelles were well developed, a striking feature being the presence of small cored vesicles (neurosecretory-type granules) measuring 100 to 260 m p in two tumors. The authors know of no report of a malignant schwannoma mentioning the ultrastructural presence of such neurosecretory-type granule^?^ As for clinical aspects,8,8)2215 of the 29 patients, in whom follow-up information was obtained, died of tumor and 14 are surviving. The compact spindle cell group appeared to have better prognosis than the myxoid group and the epithelioid group. Moreover, the entire group appeared to have more favorable prognosis than the group having von Recklinghausen’s disease. Therefore, the association of malignant peripheral nerve tumors with von Recklinghausen’s disease signifies greater malignancy in the tumor, and carries a poor prognosis.1t2,8,11 On the other hand, no apparent correlation is noted between the mitotic figures and the prognosis. Differential diagnosis includes fibrosarcoma, leiomyosarcoma, liposarcoma, malignant fibrous histiocytoma, malignant melanoma and anaplastic carcinoma.loPP The compact spindle cell type differs from fibrosarcoma and leiomyosarcoma in the following respects: the tumor cells with delicate fibrillary cytoplasmic processes tend to be arranged in less sharply interlacing bundles and fascicles than in the fibrosarcoma and leiomyosarcoma, and silver impregnation often reveals the presence of hair-like
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delicate fibrils which entwine in a sleeve-like or straight wire fashion about the tumor cells. The myxoid type differs from myxoid liposarcoma in that the tumor cells contain essentially no lipid droplets and have delicate fibrillary cytoplasmic processes. Furthermore, since the epithelioid type often mimicks malignant melanomas, carcinomas or some other central nervous tumors, one should examine the case in detail for the possible primary site in the skin or other organs.l3 Distinction from malignant fibrous histiocytoma is facilitated by the absence of the storiform pattern or cellular pleomorphi~rn.~ The development of malignant growths in cases of von Recklinghausen’s disease averaged from 6 to 16 per cent according to H O S O I ,STOUT,^' ~~ V I E T Aand ~ ~ D’AGOSTINO.~,~ In the present authors’ files, there were only 12 cases with malignant peripheral nerve tumors (4%) occurring in 291 cases of von Recklinghausen’s disease. Furthermore, 8 of these 12 cases histologically showed a t least partial areas of a neurofibroma-like pattern of the sarcoma, suggesting a malignant transformation in the neurofibromatosis. The histogenesis of malignant peripheral nerve tumors has been controversial.la, 17?1 At present, the tumors are generally considered to be derived from Schwann cells originating from the pluripotential neuroectodermal tissue (mesectoderm). Whether the Schwann cell itself retains a mesectodermal potential, or rather, that some unusual peripheral nerve tumors are derived from separate primitive mesectodermal neural crest cells that have migrated with Schwann cells out along peripheral nerve fibers, is not h0~n.4,10,12,26
References 1. D’AQOSTINO, A.N., SOULE, E.H., and MILLER,R.H.:
Primary malignant neoplasms of nerves (malignant neurilemomas) in patients without manifestations of multiple neurofibromatosis (von Recklinghausen’s disease). Cancer 16: 1003-1014, 1963. 2. D’AQOSTINO, A.N., SOULE,E.H., and MILLER, R.H.: Sarcomas of the peripheral nerves and somatic soft tissues associated with multiple neurofibromatosis (von Recklinghausen’s disease). Cancer 16: 1015-1027, 1963. 3. DASGUPTA,T.K. and BRASFIELD, R.D.: Solitary malignant Schwannoma. Ann. Surg. 171: 419428, 1970. 4.
5.
6.
7. 8. 9.
ENZINQER, F.M., LATTES,R., and TORLONI,H.: Histological Typing of Soft Tissue Tumors. International Histological Classification of Tumors, No. 3, World Health Organization, Geneva, 1969. ENZINQER, F.M. : Recent developments in the classification of soft tissue sarcomas. I n Management of Primary Bone and Soft Tissue Tumors, pp. 219-234, Year Book Medical Publishers, Chicago London, 1977. FISHER,E.R. and VUZEVSKI, V.D. : Cytogenesis of Schwannoma (neurilemoma), neurofibroma, dermatofibroma and dermatofibrosarcoma as revealed by electron microscopy. Am. J. Clin. Pathol. 49: 141-164, 1968. FORAKER, A.: Glandlike elements in a peripheral neurosarcoma. Cancer 1: 288-293, 1948. GHOSH,B.C., GHOSH, L., Huvos, A.G., and FORTNER, J.G.: Malignant Schwannoma. A A clinicopathologic study. Cancer 31 : 184-190, 1973. GORE,I.: Primary malignant tumors of nerve. A report of eight cases. Cancer 5 : 278-296, 1952.
10.
HARKIN,J.C., and REED, R.J.: Tumors of the Peripheral Nervous System. I n Atlas of Tumor Pathology, Second Series, Fascicle 3, Armed Forces Institute of Pathology, Washington, D.C., 1968.
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11. HOSOI,K.: Multiple neurofibromatosis (von Recklinghausen’s disease). Arch. Surg. 22: 258-281, 1931. 12. KARCIOGLU, Z., SOMEREN,A., and MATHES,S.J.: Ectomesenchymoma - A malignant
13. 14. 15. 18.
tumor of migratory neural crest (ectomesenchyme)remnants showing ganglionic, Schwanniae, melanocytic and rhabdomyoblastic differentiation. Cancer 39: 2486-2498, 1977. MCCORMACK,L.J., HAZARD, J.B., and DICRSON,J.A.: Malignant epithelioid neurilemoma (schwannoma). Cancer 7: 725-728, 1954. MICHEL,S.: Epithelial elements in a malignant neurogenic tumor of the tibia1 nerve. Am. J. Surg. 113: 404-408, 1967. ROSAI,J. and RODRIGUEZ, H.A.: Application of electron microscopy to the differential diagnosis of tumors. Am. J. Clin. Pathol. 50: 555-582, 1968. STEWART,F.W. and COPELAND,M.M.: Neurogenic sarcoma. Am. J. Cancer 15: 1235-1320,
1931. 17. STOUT,A.P.: The malignant tumors of the peripheral nerves. Am. J. Cancer 25: 1-38, 1935. A.P.: Fibrosarcoma. The malignant tumor of fibroblasts. Cancer 1: 3&63, 1948. 18. STOUT, 19. STOUT,A.P. and LATTES,R.: Tumors of the Soft Tissues, Second Series, Armed Forces Institute of Pathology, Washington, D.C., 1987. 20. TAKAHAMA, M.: Electron microscopic study of malignant and benign tumors of the human soft tissue. 1. Tumors of the peripheral nervous tissues. Bull. Tokyo Med. and Dent. Univ. 1983. I.M.: Origin of penneural fibroblastoma. Am. J. Pathol. 16: 3340, 1940. 21. TARLOV, E. : Malignant peripheral nerve tumors. A clinicopathological study of twenty 22. UCHIHARA, cases. Acta Med. Shikoku 29: 1-10, 1973 (in Japaneae). 23. VIETA,J.O. and PACK, G.T.: Malignant neurilemomas of psripheral nerves. Am. J. Surg. 82: 41-31, 1951. 24. WAQQENER, J.D. : Ultrastructure of benign peripheral nerve sheath tumors. Cancer 19: 899-709, 1968. 25. WOODRUFIT, J.M. : Peripheral nerve tumors showing glandular differentiation (glandular Schwannomes). Cancer 37: 2399-2413, 1978.
PRIMARY MALIGNANT PERIPHERAL NERVE TUMORS (MALIGNANT SCHWANNOMAS) A Clinicopathologic and Electron Microscopic Study Masazumi TSUNEYOSRI and Munetomo ENJOJI The Becond Department of Pathology, Faculty of Medicine, Kywhu University (Received on Aug. 18, 1978)
A clinicopathologic and electron microscopic study was performed on 35 cases of primary malignant peripheral nerve tumors, among which 12 developed in association with neurofibromatosis (von Recklinghausen's disease) and further 11 in keeping with anatomically discernible nerves in patients without neurofibromatosis. Depending upon the histologically predominant pattern, these tumors were subdivided into three groups: 23 compact spindle cell, 6 myxoid, and 6 epithelioid varieties of the tumor. The common ultrastructures in three of the 35 tumors were as follows: 1) The cell membranes manifested characteristic infoldings and lamellar configuration. 2) The tumor cell surfaces were coated by occasional basal lamina or homogeneously electrondense membranous material. 3) The cytoplasms contained well-developed organelles and a few neurosecretory-type granules. Differential points from other soft-tissue sarcomas were briefly discussed on the histologic basis. ACTA PATH. JAP. 29: 363-375, 1979.
Introduction
Primary malignant tumors of peripheral nerves are comparatively rare but exhibit a variety of clinical and histologic appearances. Since the epochal work of STEWART and COPELANDin 1931,1a there has been much discussion about the clinicopathologic features and biologic behavior of the tumors.3~8~10~17~2a~23 The whole scope of the tumors, however, is not as yet defined. The present authors, therefore, undertook a clinicopathologic review of 35 lesions interpreted as malignant peripheral nerve tumors. Of the 36 tumors, 12 developed in association with neurofibromatosis (von Recklinghausen's disease) including seven cases with anatomical localization of the tumor in peripheral nerves, and 11 other tumors were related anatomically to discernible nerves in patients without neurofibromatosis. Three of the 36 tumors were studied electron microscopically by contrasting the fine structures in a normal peripheral nerve, three neurilemomas and four neurofibromas. E27 iEB, B%Z? R h Supported by Grants-in-aid for Cancer Research 1976 and 1977 from the Ministry of Health and Welfare and 1977 from Ministry of Education, Science and Culture of Japan and by Grant from the Fukuoka-ken Anti-Cancer Association, 1976. Mailing address: Dr. M. ENJOJI,Second Department of Pathology, Faculty of Medicine, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812, Japan. 363
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Materiak and Methods The source of materials for this study is about 7,000 cases of soft-tissue tumors in the files of the Second Department of Pathology, Faculty of Medicine, Kyushu University. The registry now covers the period 1956-1976,end there were 36 cases of malignant tumors of peripheral nerves. Of the 35 tumors, 23 developed in association with von Recklinghausen’s disease or involved anatomically discernible nerve& Furthermore, 12 additional cases, though lacking such association as mentioned above, were selected because the tumor exhibited the microscopic features which convinced us of nerve origin and malignant nature, closely resembling the features in the foregoing cases. All of the paraffi blocks available were recut and stained with hematoxylin and eosin. Special stains employed when necesaary included Masson’s trichrome stain, silver impregnation for reticulin, alcian blue and PAS stains, Bodian’s nerve fiber, stain, Sevier-Munger neural tissue stain, Fontana stain for melanin, and Grimelius stain for argyrophil granules. Fresh tissues for electron microscopy were available in three cases of the malignant peripheral nerve tumor. The tissues were fixed in 3% glutctraldehyde solution (buffered pH 7.4) end were postfixed in 1% phosphate-buffered osmium tetroxide. Following dehydration the tissue blocks were embedded in Epon 812 and were cut on an LKB ultrotome 111. The sections were stained with urenyl acetate and lead citrate. The electron microscope used was a JEM 100 C. I n addition, frmh tissues from a normal ulnar nerve, three neurilemomasand four neurofibromas were prepared by the same method for comparative electron microscopy.
Clinical Features Sea: and Age Of the 35 patients, 11 were males and 24 were females. The age of the patients ranged from 11 to 86 years with the mean of 40 years (Fig. 1).
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Anatomical Site The tumors were attached anatomically to peripheral nerves in 18 of the 36 cases. Eleven tumors (31%) were located in the lower extremities, 10 (29%) in the upper extremities, 7 (20%) in the trunk, 3 in the retroperitoneum, 2 in the head and neck region and 2 in other sites (Fig. 2). There is none of multiple primary tumors.
C l i n h l History A swelling or lumpy mass was almost always the chief sign to attract the patient’s attention. In 21 of the 35 patients, the masses were associated with pain. Of the 35, 12 (34%) had developed in association with neurofibromatosis (von Recklinghausen’s disease), including seven cases with a tumor closely connected anatomically to grossly discernible peripheral nerves. Of the 23 cases unassociated with neurofibromatosis, 11 had a close anatomical relation to discernible nerves. Fig. 1. Frequency in various decades and sexes.
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Fig. 2. Anatomical distribution.
Pathology Macroscop.ic Observations The size of tumors a t the time of the first excision varied from a small-finger’s tip to a child’s head. Grossly, the tumor was well circumscribed in 22 patients (73%) and showed infiltrating growth in 13 (27%). The consistency was usually described as elastic soft. The cut-surface was either parenchymatous or myxomatous with gray-white to gray-yellow color (Fig. 3).
Light Mioroscopic Pindings Histologic features showed a considerable variety. The tumors were usually composed predominantly of plump, spindle, mononuclear cells admixed with a small number of round and polygonal cells. These cells were packed in interlacing or fascicular bundles, showing
Fig. 3. Typical gross appearance consisting of a multilobulated graywhite tumor within the ulnar nerve of a 51-year-old woman.
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complicated loose and dense arrangements or sometimes a “herring-bone” pattern. Occasionally, the tumors had a myxoid matrix, or an undulating or a perithelial pattern of tumor cells. Not infrequently in others or in different portions of the same growth, there were peculiar and distinct alignments of tumor cells in epithelioid structures. Nuclear palisading appeared clearly in six cases (Fig. 4). Gland-like s t r u ~ t u r e s ~ , ~ ~ , 2 5 lined by columnar or cuboidal cells were identified in two cases. In eight cases (23%), there existed a neurofibroma-like pattern in some portions of the tumor (Fig. 6). The tumor cells were spindle, polygonal or round in shape and usually showed certain uniformity. Only occasionally, however, there were foci of pleomorphism of tumor cells, and in seven cases (20%) giant cells of mononucleate and multinucleate types were sparingly distributed throughout the neoplastic tissue. The number of mitoses averaged three with a range from zero to 10 per each high-power field. Small calcium deposits were identified in two tumors. There were also occasional areas of hemorrhage and necrosis in the tumors. Although there was such a variation as mentioned above in histologic appearance in the malignant peripheral nerve tumors, the tumors could be divided reasonably into the following three groups depending upon the predominant or most striking pattern of each tumor: 1) compact spindle cell group, 2) myxoid group and 3) epithelioid group (Table 1). Table 1. Histological Claaa$cation
No. pt.
% Pt.
23
66
3. Epithelioid group
6 6
17 17
Total
36
100
Histological type 1. Compact spindle cell group 2. Myxoid group
Compact Spindle Cell Group (23 m e s ) The tumors in this group were composed of plump or slender spindle cells (Fig. 6). The cells were compactly arranged in bundles that produced interlacing fascicles, often exhibiting palisading, herring-bone or some other particular patterns, The tumor cells showed a fair uniformity. They had faintly acidophilic, scanty or moderately abundant cytoplasm possessing delicate fibrillary processes. The nuclei of the tumor cells were commonly of an oval or more elongated shape with smooth surfaces and rather thin nuclear membranes. The nuclear chromatin was diffusely stippled. Some of the tumors in this group were composed predominantly slender spindle cells with collagen production and were reminiscent of fibrosarcoma. In rare instances, the characteristic feature was perivascular growth of tumor cells with proliferation of vascular endothelial cells. I n one case, there were tophus-like depositions of hyaline, showing radial arrays of tumor cells (Fig. 7).
Myxoid Group (6 cases) The tumor cells were gathered in complicated loose and dense areas. The feature of the dense areas is essentially similar to those of the
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Fig. 4. Nuclear palisading identified in the tumor of the same case as Fig. 3.H & E, x 110. Fig. 5. Neurofibroma-like pattern identified in some area of an epithelioid type tumor. H & E, x 91. Fig. 6. Compact spindle cell type arising in the tibia1 nerve with von Recklinghausen’s disease. The tumor cells are compactly arranged in fascicles (H & E, x 180). The inset shows the presence of wavy and delicate hair-like fibrils about the tumor cells. Silver impregnation for reticulin, x 450. Fig. 7. Tophus-like depositions of hyaline showing radial arrays of tumor cells identified in the tumor of a 21-year-old woman. H & E, 136.
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Fig. 8. Myxoid type arising in the sciatic nerve. The tumor cells reveal complicated loose and dense arrangement. Predominant myxoid areas consisting of pools hyaluronidase-sensitive acid mucopolysaccharide is a common finding. H t E, x 90. Fig. 9. Epithelioid type arising in the iilnar nerve with von Recklinghausen’s disease. Epithelial cell-like cells are arranged in small solid nests. H t E,
x 105. Fig. 10. Glandular variant of epithelioid type in the sciatic nerve with von Recklinghausen’s disease. Predominant areas consist of epithelioid arrangement with scattering atypical gland-like structures. H BE E, x 350.
compact spindle cell group. In the loose areas, however, the spindle tumor cells were loosely arranged in interlacing or streaming, sometimes undulating fascicles or in reticular networks, and were separated individually by a myxoid matrix (Fig. 8). The perithelial arrangement of atypical round or spindle cells with plump nuclei was sometimes prominent. The myxoid matrix were stained for acid mucopolysaccharides with
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alcian blue. A neurofibroma-like pattern was often a counterpart of this type and was identified at least in some portions of the tumor. The tumor cells were bipolar spindle cells or stellate cells with anastomosing plasmatic processes which tended to form a syncytial network. The cytoplasm was fibrillary and brightly acidophilic. There were occasional giant cells of mononucleate and multinucleate types. These cells had delicate fibrillary cytoplasmic processes, and had neither lipid droplets nor cross striations in their cytoplasm. Epithelioid group (6 cases) All the tumors of this group arose in anatomically discernible nerves or in somatic soft tissue in association with neurofibromatosis. In areas of epithelioid structures, the tumor cells were round, polygonal, plump or spindle and were arranged in solid nests, clusters or whorls (Fig. 9). The tumor cells were often intimately related to thin vascular channels. Some had abundant cytoplasm that was either pale or eosinophilic and homogeneous. The tumor cells frequently contained large nuclei with prominent nucleoli. The cell type and the arrangement simulated the appearance of nonpigmented areas of a malignant melanoma. One case, which could be classified as another rare type “glandular type”, showed unique foci of glandular differentiation, cellular portion of the tumor containing atypical gland-like structures lined by epithelial-like pseudostratified columnar or nonciliated cuboidal cells (Fig. 10). Histochemical Findings
Silver impregnation for reticulin or Bodian’s nerve fiber stain revealed the presence of wavy and delicate hair-like fibrils which entwined in a sleeve-like or straightwire fashion about tumor cells (Fig. 6). Alcian blue positive material was identified among the loosely arranged tumor cells. Neither PAS-positive material nor lipiddroplets were identified in the cytoplasm of the tumor cells. There was no Grimelimpositive granules in tumor cells either. Electron Microscopic Findings (3 Cases)
The tumor cells were polygonal mononucleated cells or plump spindle cells. The cell membranes were of indefinite morphology. Some cells exhibited characteristic whorl-like or lamellar structures resembling Schwann cells of Antoni type A neurilemoma t i s s ~ (Figs. e ~ ~ 11 ~ and ~ 12), while others had pseudopodia-like, finger-like or bubblelike structures resembling those of Antoni type B neurilemoma tissue or of neurofibroma 20~24(Fig. 13). Prominent myelin figures and pinocytotic vesicles were identified in the cell membranes in one case (Fig. 12a). The tumor cells were partly surrounded by basement membrane or homogeneous electron dense membranous material in three cases (Figs. 12b and 13). The nuclei of the tumor cells were round or ovoid in shape, smooth in outline with occasional invaginations in their membranes. Chromatin was of an even distribution. Nuclei-cytoplasmic ratio of tumor cells was high as shown in light microscopy. Among cytoplasmic organelles, large aggregates of small vesicles and free ribosomes were frequently observed together with scattered mito-
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Fig. 13. Electron micrograph of a case arising in the brachial nerve. Right: Irregular infoldings of the cytoplasmic processes with occasional lamina of basement membranous material. x 9,600. Upper left: A portion of tumor cell surrounded by the basal lamina. x 42,500. Lower left: Light micrograph of the same case. H &, E x 440.
chondria, Golgi apparatus, endoplasmic reticulums and intracytoplasmic microfibrils. In two cases of compact spindle cell type, a characteristic feature was the presence of intracytoplasmic cored vesicles (neurosecretory-type granules) measuring 100 to 260 mp in diameter. In one such case focal aggregations of intracytoplasmic cored vesicles were observed (Fig. 14), while in the other case a very small number of cored vesicles was identified in tiny areas. Extracellular space contained a wide assortment of structural components, including numerous bundles of collagen, microfibrils and amorphous material. Treatment and Prognosis
There was tumor recurrence in 24 (68%) of the 35 patients. Twenty-two of the 28 instances treated solely by simple excision recurred, the first recurrence occurring within 1.5 years in nearly all patients. Metastases were identified in 10 (29%) of the 35 cases. The commonest site of metastasis was the lung. Fig. 11. Electron micrograph of a compact spindle cell type showing nuclear palisading seen in Fig. 4. The cell membranes show characteristic lamellar infoldings. x 9,140. Fig. 12. High magnification of Fig. 11. Pinocytotic vesicles (a), and lamina of bmement membranous material (b)are prominent. Fig. 8. x 67,600; Fig. b, x 32,500.
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Fig. 14. Electron micrograph of a cellular area of the same case as Fig. 4. Several dense core secretory granules (arrow) are found in the clear cytoplasms. x 4,670. The inset is a high magnification of the cytoplasmic granules measuring 100 to 200 mp in diameter. x 41,400.
All 35 patients had been treated surgically, the operation being radical in four patients. Of the 29 patients in whom follow-up information was obtained, 15 died of tumor between 4 months and 5 years after initial treatment and 14 patients are surviving. Out of the 14 survivors, five are living for more than five years. The five-year survival rate of all cases was 30%. In the compact spindle cell group, seven of the 23 patients have died and eleven are surviving. In the myxoid group, four of the six have died and one surviving for three years. In the epithelioid group, four of the six have died and two surviving. Out of the 12 patients having neurofibromatosis, three were living and well and seven died of the disease at the end of the follow-up period. DiScuSsiolz
Primary malignant tumors of peripheral nerve had relatively variable clinical and morphologic features. Nevertheless, since early-day review of malignant peripheral nerve tumors by STEWARTand COPELAND(1931)l”there have as yet been no conclusive results for their clinicopathologic features and biological behavior of the tumors. According to the WHO histological classification of soft-tissue tumors in 196g4, the term “malignant tumors of peripheral nerves” specifies the following categories: 1)
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malignant schwannoma (neurogenic sarcoma, neurofibrosarcoma), and 2) peripheral tumors of primitive neuroectoderm. The tumors the present authors were dealing with in this study were in reality malignant schwannomas. They have divided the tumors into the following three groups with descriptive terms on a histologic basis (Table I ) : 1) compact spindle cell, 2) myxoid, and 3) epithelioid. In this series, the compact spindle cell type occurred most commonly and in 23 cases (66%). The myoxid type bearing a superfkial resemblance to myxoid liposarcoma or myxoid malignant fibrous histiocytoma appeared in 6 cases (17%). The epithelioid type occurred in 6 cases (17%)4. Some tumors of this type were reminiscent of malignant melanoma because of their epithelioid character, though failing to show melanin pigment?JO,lS One of the cases showed unique foci of atypical gland-like structures lined by epithelial-like pseudostratified nonciliated cells, the features being consistent with those in “glandular schwannoma” reported by WOOD RUFF.^^ Under electron microscopy the tumor cells, despite of the variation in differentiation, often showed fundamental characteristics of Schwann cells. It was noteworthy that very characteristic features of the tumor cells consisted in the formation of cytoplasmic processes and in the structure of their cell membranes.6,20 The cell membranes exhibited characteristic infoldings and lamellar configuration. In particular, one case of the compact spindle cell type showing a histological pattern of nuclear palisading was characterized ultrastructurally by prominently lamellar or whorl-like infoldings of cell membranes which resembled those of Schwann cells in Antoni type A neurilemoma tissue. 6~w),24 Occasional myelin formation in cell membranes was identified. The presence of basal lamina or homogeneously electron dense membranous material which coated the exposed cell surface, was another major factor in excluding identification from a fibroblast. The intracytoplasmic organelles were well developed, a striking feature being the presence of small cored vesicles (neurosecretory-type granules) measuring 100 to 260 m p in two tumors. The authors know of no report of a malignant schwannoma mentioning the ultrastructural presence of such neurosecretory-type granule^?^ As for clinical aspects,8,8)2215 of the 29 patients, in whom follow-up information was obtained, died of tumor and 14 are surviving. The compact spindle cell group appeared to have better prognosis than the myxoid group and the epithelioid group. Moreover, the entire group appeared to have more favorable prognosis than the group having von Recklinghausen’s disease. Therefore, the association of malignant peripheral nerve tumors with von Recklinghausen’s disease signifies greater malignancy in the tumor, and carries a poor prognosis.1t2,8,11 On the other hand, no apparent correlation is noted between the mitotic figures and the prognosis. Differential diagnosis includes fibrosarcoma, leiomyosarcoma, liposarcoma, malignant fibrous histiocytoma, malignant melanoma and anaplastic carcinoma.loPP The compact spindle cell type differs from fibrosarcoma and leiomyosarcoma in the following respects: the tumor cells with delicate fibrillary cytoplasmic processes tend to be arranged in less sharply interlacing bundles and fascicles than in the fibrosarcoma and leiomyosarcoma, and silver impregnation often reveals the presence of hair-like
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delicate fibrils which entwine in a sleeve-like or straight wire fashion about the tumor cells. The myxoid type differs from myxoid liposarcoma in that the tumor cells contain essentially no lipid droplets and have delicate fibrillary cytoplasmic processes. Furthermore, since the epithelioid type often mimicks malignant melanomas, carcinomas or some other central nervous tumors, one should examine the case in detail for the possible primary site in the skin or other organs.l3 Distinction from malignant fibrous histiocytoma is facilitated by the absence of the storiform pattern or cellular pleomorphi~rn.~ The development of malignant growths in cases of von Recklinghausen’s disease averaged from 6 to 16 per cent according to H O S O I ,STOUT,^' ~~ V I E T Aand ~ ~ D’AGOSTINO.~,~ In the present authors’ files, there were only 12 cases with malignant peripheral nerve tumors (4%) occurring in 291 cases of von Recklinghausen’s disease. Furthermore, 8 of these 12 cases histologically showed a t least partial areas of a neurofibroma-like pattern of the sarcoma, suggesting a malignant transformation in the neurofibromatosis. The histogenesis of malignant peripheral nerve tumors has been controversial.la, 17?1 At present, the tumors are generally considered to be derived from Schwann cells originating from the pluripotential neuroectodermal tissue (mesectoderm). Whether the Schwann cell itself retains a mesectodermal potential, or rather, that some unusual peripheral nerve tumors are derived from separate primitive mesectodermal neural crest cells that have migrated with Schwann cells out along peripheral nerve fibers, is not h0~n.4,10,12,26
References 1. D’AQOSTINO, A.N., SOULE, E.H., and MILLER,R.H.:
Primary malignant neoplasms of nerves (malignant neurilemomas) in patients without manifestations of multiple neurofibromatosis (von Recklinghausen’s disease). Cancer 16: 1003-1014, 1963. 2. D’AQOSTINO, A.N., SOULE,E.H., and MILLER, R.H.: Sarcomas of the peripheral nerves and somatic soft tissues associated with multiple neurofibromatosis (von Recklinghausen’s disease). Cancer 16: 1015-1027, 1963. 3. DASGUPTA,T.K. and BRASFIELD, R.D.: Solitary malignant Schwannoma. Ann. Surg. 171: 419428, 1970. 4.
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ENZINQER, F.M., LATTES,R., and TORLONI,H.: Histological Typing of Soft Tissue Tumors. International Histological Classification of Tumors, No. 3, World Health Organization, Geneva, 1969. ENZINQER, F.M. : Recent developments in the classification of soft tissue sarcomas. I n Management of Primary Bone and Soft Tissue Tumors, pp. 219-234, Year Book Medical Publishers, Chicago London, 1977. FISHER,E.R. and VUZEVSKI, V.D. : Cytogenesis of Schwannoma (neurilemoma), neurofibroma, dermatofibroma and dermatofibrosarcoma as revealed by electron microscopy. Am. J. Clin. Pathol. 49: 141-164, 1968. FORAKER, A.: Glandlike elements in a peripheral neurosarcoma. Cancer 1: 288-293, 1948. GHOSH,B.C., GHOSH, L., Huvos, A.G., and FORTNER, J.G.: Malignant Schwannoma. A A clinicopathologic study. Cancer 31 : 184-190, 1973. GORE,I.: Primary malignant tumors of nerve. A report of eight cases. Cancer 5 : 278-296, 1952.
10.
HARKIN,J.C., and REED, R.J.: Tumors of the Peripheral Nervous System. I n Atlas of Tumor Pathology, Second Series, Fascicle 3, Armed Forces Institute of Pathology, Washington, D.C., 1968.
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11. HOSOI,K.: Multiple neurofibromatosis (von Recklinghausen’s disease). Arch. Surg. 22: 258-281, 1931. 12. KARCIOGLU, Z., SOMEREN,A., and MATHES,S.J.: Ectomesenchymoma - A malignant
13. 14. 15. 18.
tumor of migratory neural crest (ectomesenchyme)remnants showing ganglionic, Schwanniae, melanocytic and rhabdomyoblastic differentiation. Cancer 39: 2486-2498, 1977. MCCORMACK,L.J., HAZARD, J.B., and DICRSON,J.A.: Malignant epithelioid neurilemoma (schwannoma). Cancer 7: 725-728, 1954. MICHEL,S.: Epithelial elements in a malignant neurogenic tumor of the tibia1 nerve. Am. J. Surg. 113: 404-408, 1967. ROSAI,J. and RODRIGUEZ, H.A.: Application of electron microscopy to the differential diagnosis of tumors. Am. J. Clin. Pathol. 50: 555-582, 1968. STEWART,F.W. and COPELAND,M.M.: Neurogenic sarcoma. Am. J. Cancer 15: 1235-1320,
1931. 17. STOUT,A.P.: The malignant tumors of the peripheral nerves. Am. J. Cancer 25: 1-38, 1935. A.P.: Fibrosarcoma. The malignant tumor of fibroblasts. Cancer 1: 3&63, 1948. 18. STOUT, 19. STOUT,A.P. and LATTES,R.: Tumors of the Soft Tissues, Second Series, Armed Forces Institute of Pathology, Washington, D.C., 1987. 20. TAKAHAMA, M.: Electron microscopic study of malignant and benign tumors of the human soft tissue. 1. Tumors of the peripheral nervous tissues. Bull. Tokyo Med. and Dent. Univ. 1983. I.M.: Origin of penneural fibroblastoma. Am. J. Pathol. 16: 3340, 1940. 21. TARLOV, E. : Malignant peripheral nerve tumors. A clinicopathological study of twenty 22. UCHIHARA, cases. Acta Med. Shikoku 29: 1-10, 1973 (in Japaneae). 23. VIETA,J.O. and PACK, G.T.: Malignant neurilemomas of psripheral nerves. Am. J. Surg. 82: 41-31, 1951. 24. WAQQENER, J.D. : Ultrastructure of benign peripheral nerve sheath tumors. Cancer 19: 899-709, 1968. 25. WOODRUFIT, J.M. : Peripheral nerve tumors showing glandular differentiation (glandular Schwannomes). Cancer 37: 2399-2413, 1978.
