Acta neuropath. (Berl.) 33, 333 9 by Springer-Verlag 1975

342 (1975)

Primary Rhabdomyosarcomaof the Central Nervous System* Basile Pasquier, Pierre Couderc, D o m i n i q u e Pasquier, P a n h Meng H o n g a n d J a c q u e s Pellat** Department of Pathology (Pr. P. Couderc) C.H.U. de Grenoble, La Tronche 38700, France Received July 30, 1975; Accepted October 10, 1975

Summary. A case of primary rhabdomyosarcoma in the brain stem is described in an 8 year old girl. The clinical data showed a right side hemiplegia then a total paralysis of the left sixth cranial nerve and a paraplegia which became lethal in 3 months. The necrospy revealed a tumoral nodule in the left medulla oblongata and pons with diffuse subarachnoidal extension from the cranial nerves to the cauda equine roots. Histologically the tumor appeared to be polymorph with numerous rhabdomyoblasts which had a clear cross striation and which were sometimes less differentiated without any neuronal or glial elements. Perivascular tumoral cells and blood vessels were closely linked, the Virchow-Robin spaces were clearly involved. The electron microscopic study confirmed that tile less differentiated cells were of a rhabdomyoblastic nature. A review of the litterature indicates that these malignant neoplasias are highly exceptional, and can be classified within the group of primary tumors of the neuraxis with muscular elements. The histogenetic origin of these tumors appears to be the ectomesenchyme of neural crests. Key words: Brain tumor -- Rhabdomyosareoma -- Ectomesenchyme of the neural crests -- Embryonal sarcoma.

Introduction The l e p t o m e n i n g e a l or i n t r a c r a n i a l e x t e n s i o n of e m b r y o n a l sarcomas w i t h r h a b d o m y o b ] a s t i c differentiation o r i g i n a t i n g i n the n a s o p h a r y n x , face, or middle ear is well k n o w n b u t rare (Meyer a n d Reah, 1953; Ma]amud, 1957; H o r n a n d E n t c r l i n e , 1958; l~ussell a n d R u b i n s t e i n , 1959; Masson, J. K., 1965; Miller a n d Dalager, 1974). A p a r t from some p i n e a l b o d y area d y s e m b r y o m a s (Cabanne, 1965; Jellinker, 1973; Marsden, 1974), it is more seldom to observe the whole or p a r t of a p r i m a r y t u m o r of the c e n t r a l n e r v o u s s y s t e m or its sheaths made of i m m a t u r e o r / a n d m a t u r e s t r i a t e d muscle fibers. This possibility, b a c k e d with clinical, pathological a n d electron microscopic studies, has been described i n this r e p o r t which will be followed b y a few c o m m e n t s on the histogenesis of this p r i m a r y mesene h y m a l t u m o r of the brain. 1

Glinieal History Corinne BEL. eight years old (born december 24, 1965) had no pathological history. There was no apparent signs of phakomatosis in her family. At the end of november 1973, she complained of morning headaches, then suddenly of a right side hemiparesis with diplopia. On physical examination, the findings were the following: right hemiplegia which did not affect * Our special thanks to 2r Chantal ~Niariottewho took care of the translation. ** Department of Neurology (Pr. Ag. J. Perret). 1 The authors wish to thank Pr. R. Escourolle; M. Toga; :~I.Tommasi and L. J. l~ubinstein for their advices.

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the face, right deep hyloerrefiexia a n d ]3abinski sign, then total paralysis of left sixth cranial nerve. E x a m i n a t i o n of other systems, fundus of the eye, radiography of the skull a n d rachis, revealed no noteworthy findings. The l u m b a r puncture showed 10 cells per 3 m m and 480mg/ml protein, b u t the cytological e x a m i n a t i o n revealed the presence of " m a l i g n a n t cells of unknown origin". The echoencephalogram, electroencelohalogram , left carotid a n d humeral anglogram, pneumoencephalography with s t r a t i g r a p h y of the b r a i n stem were normal. The diagnosis of a m a l i g n a n t t u m o r of the loons a n d medulla oblongata seemed possible. A corticot h e r a p y a n d a cobalt t h e r a p y (centered on the posterior cerebral fossa) brought about a t e m p o r a r y improvement. On March, 17, 1974, a sudden flaccid paraplegia appeared. The cerebrosloinal fluid obtained b y suboccipital p a t h w a y was xanthocromic, containing 3000 mg/ml protein (the new l u m b a r puncture was a failure). A laminectomy (L1 to Ld) revealed a strained dura mater, a swollen lelotomeninx a n d a distension of all the roots of the cauda equine. The biopsy of lelotomeninges (reference 74 G 74326) appeared to be difficult to interpret, b u t confirmed t h a t the process involved a m a l i g n a n t tumor. The girl died 3 months after the first symptom, owing to generalized convulsions. P a t h o l o g i c a l D a t a ( R e f e r e n c e 74 G 7 4 5 3 0 ) The post m o r t e m was carried out very soon after d e a t h a n d did not show a n y other t u m o r t h a n the one in the central nervous system.

1. Gross Study The dura m a t e r was normal, a n d the superior sagittal sinus not obstructed. The brain, which weighed fresh 1350 g, was oedematous. The most conspicuous abnormalities were located in the b r a i n stem a n d the spinal cord. F r o m the outside, one could see a Ieft tumefaction of the medulla oblongata and pons which pushed forward and to the right the basilar artery and the left vertebral artery. All the leptomeninx of the anterior surface of the brainstem was thickened. This white firm vicissitude covered the emergence of most of the cranial nerves, which could not be identified anymore, except for the trigeminal nerve. It reached upward and forward the ponto-erural junction and laterally the two eerebello loontine angles, backward, the cerebellum, downward the spinal canal, covering the rachidian and cauda equine roots; consequently the spinal medulla appeared to be bamboo-like. The frontal sections of the cerebrum showed a global ventricular dilatation, b u t there was no t u m o r in the suloratentorial area, where the ]eptomeninx was normal on gross examination. The pineal body was also normal. Transverse sections of the b r a i n stem a n d cerebellum confirmed the presence of a white and firm tumoral nodule, its diameter varied from 1/2 to 1 cm according to the level of the section. I t grew from the lower left p a r t of the pons (Fig. 1 a), then on to the anterior left hemibulb from the p y r a m i d to the inferior olive (Fig. 1 b). This tumor, well defined on the back, mixed with the lelotomeninx on the front-side. The cerebellum (vermis a n d hemispheres) showed no tumor, b u t the fourth ventricle was very distended. I n the spinal cord the leptomeningeal t u m o r infiltration could be up to i cm thick. There was no intra-medullary softening or tumor. The dura m a t e r was also normal in this area.

2. Light Microscopy Study This s t u d y was carried out on numerous blocks of the t u m o r coming from the most interesting areas of the neuraxis, embedded in paraffin a n d coloured according to the following stainings: hemalum, phloxin, saffron (HPS), Masson's trichrome, lgegaud's ferric hematoxylin, Laidlaw's silver carbonate impregnation for reticulin, Glees a n d Marsland's silver impregn a t i o n for neuroglia, Well a n d Davenporffs method for gliomas, Loyez's, iNissl's, Biclchowsky's method, Mallory's phosphotungstic acid h e m a t o x y l i n (P.T.A.H.). The study made it possible to identify the histological type of the t u m o r a n d to u n d e r s t a n d its modalities of extension, b u t could not determine its starting point.

a) Nervous Parenchyma The sections of the encelohalon showed no tumoral proliferation either in the nervous tissue or in the meninges. I t was essentially the anterior left hemibulb a n d the lower left loons

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Fig. 1. (a) Pons (transverse section) left anterior tumoral nodule, distension of the fourth ventricle (no 74 G74530, Loyez's stain). (b) l~edulla oblongata (transverse section): left anterior and leptomeningeal tumor. The cerebellum is normal (Loyez's stain). (c) Histological pattern of the tumor. Ribbon-like elements with cross-striations (->) and less differentiated cells. (PTAH, • 180). (d) Rhabdomyoblasts (Loyez's stain, • 1 125)

which were affected. This tumor consisted of two main types of cell. First, there were small cells with ill defined limits, their nuclei were round or ovoid, light and vesicular or sometimes dark with scarse cytoplasm,

slightly eosinophilic.

The protoplasms

were more

or less ~eido-

philic according to the size of the cell. The irregular distribution of the ehromatin (small dark

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Fig. 2. (a) Bundles of undifferentiated cells a n d multinucleated giant cells (trichrome's Masson, • 360). (b) Mierofilamentous bundle (m]) in a n u n d i f f e r e n t i a t e d cell. ( • 9297)

bundles) gave to the nuclei t h e i r peculiar spotted or striped appearance. Second, the very large fusiform or ribbon-like elements were packed together in bundles. They were strongly eosinophilic a n d Mallory's, Loyez's a n d Masson's stainings clearly showed cross-striations (:Fig. 1 d). Their nuclei were larger, central or eccentric, single or multiple, often fusiform a n d always spotted. All those elements were in m a n y cases distributed in nodules or in bundles, often b u t n o t always a r o u n d a vessel, in the Virchow-I~obin spaces. Mitosis were not frequent. The stroma was not a b u n d a n t , poor in eollagenous a n d reticular fibers. The vessels were more or less numerous. I n the middle of the m a i n tumoral nodule there were m a n y capillaries w i t h regular walls surrounded b y calcifications which reminded of calcospherites. There was a subcentral necrotic area surrounded b y spumous clear cells with d a r k nucleus. The Nissl's staining was negative. The maj or p a r t of the glial fibers a n d of the normal neurons of the nervous tissue was pushed back on the peripheral area, where a n astrocytic gliosis was easily observed. Sometimes some rhabdomyoblasts crept into a glial bundle. This ponto-bulbar t u m o r was directly linked w i t h the leptomeninges.

b) Leptomeninges The t u m o r structure became more polymorphic b u t the cell types were identical a n d their density higher. I t was for the major p a r t a fasciculated flbrosarcomatous-like proliferation, consisting of mixed bundles a n d striated ribbon-like elements. Sometimes b u t more seldom, it became areolar or myxoid. The necrotic areas r e m a i n e d rare, the vessels were not numerous, the collagenous a n d reticular network was poor. A p a r t from small round cells with light spotted or dark nuclei, a n d numerous rhabdomyoblasts, some unusual features were observed: multimmleated giant cells with spotted crowded nuclei (:Fig.2a), strongly eosinophilic vacuolar striated cytoplasm a n d fusiform processes; bizarre, tadpole, racket-shaped or filiform cells

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(they were longer than the longest field of the microscope). There were more and more mitosis. Here and there one could observe voluminous round elements with irregular and strongly ehromophilic nuclei, highly aeidophilic cytoplasm where cross-striations did not show very well, except on the periphery. Whenever they were not pycnotic, the nuclei had a striking common characteristic which was the very peculiar distribution of the chromatin, responsible for their spotted appearance. The extension reached the basilar artery, the vertebral arteries, the various cranial nerves, the two ecrebello-pontine angles, the cerebellar leptomeninx, the deepest part of the ehoroid plexus, and the subependymal area of the floor of the fourth ventricle. Above, it spotted at the pontocrural junction, below at the terminal dural cul-de-sac. It spread to the Virchow-Robin spaces and also to the rachidian and eauda equine roots. There was not intra-medullar softening or sareomatous localization.

3. Electron Microscopy Study (Pr. At. P. Stoebner) This examination was performed on the leptomeninges obtained during the post-mortem and fixed in formalin, using the usual electron microscopic techniques, which were applied at a late stage. Two findings should be mentioned, on one hand, there existed a homogeneous tumoral population of a myoblastic type, on the other hand, it seemed to consist of paucicellular bundles limited by "basal material".

a) Tumor Cells Structure The major part of the cells measured between 7 and 15 ~z" and contained specific microfiIamentous bundles (Fig.2b). Those microfilaments were either distributed at random (Fig. 3 a) or organised in myofibrils (Fig. 3 c) which could be identified by their cross striations with primitive Z band formation.

b) Tumor Cells Distribution Myoblastic cells were closely linked together and with the vessels. Paucicellular bundles were frequently observed. The microfilamentous bundles were still surrounded by some cytoplasm and formed dense moulds as compared to the clear-centred nucleithe chromatin of which was marginated. The ceils were separated by a thin coat of a regular poorly osmiophilic material of a "basal type" (Fig. 3b). Tumor cells were often located right next to capillaries, arterioles, venules; there was no continuity between the "basal peritumoral and basal perivascular materials", (pericyts and leiomyocyts). There were always a few collagenous fibers to separate those two structures even when a tumoral myoblastic cell had penetrated into a vascular wall.

Discussion

A. Pathological, Clinical and Diagnostic Comments This p a t h o l o g i c a l f e a t u r e s i m p l y t h e diagnosis of a r h a b d o m y o s a r c o m a . T h e absence of a n y t u m o r in t h e viscera, m e a t u s acousticus i n t e r n u s a n d face is strongly in f a v o r of a p r i m a r y t u m o r of t h e c e n t r a l n e r v o u s system. This e l i m i n a t e s t h e i n t r a c e r e h r a l e x t e n s i o n of some e m b r y o n a l s a r c o m a s of t h e child. T h e o n l y unsolved p r o b l e m is t h e s t a r t i n g p o i n t : i n t r a p a r e n c h y m a l ? l e p t o m e n i n g e a l ? or a t t h e ex p en s e o f a cranial n e r v e ? T h e clinical d a t a ar g u e s t r o n g l y in f a v o r o f a p r i m a r y l o c a l i z a t i o n in t h e b r a i n stem. A f t e r a r e v i e w of t h e l i t e r a t u r e , we were able t o collect, l e a v i n g aside p i n e a l b o d y t u m o r s , t w e n t y t h r ee eases of p r i m a r y neoplasms of t h e n e u r a x i s consisting e x c l u s i v e l y or in part. of a s m o o t h or s t r i a t e d muscular component. 2 2 A new case has been reported since the drafting of this report: Vuia. 0., Hager, H.: Central neuroblastic tumor associated with smooth muscle fibers. A study with the optic and electron microscopes. Europ. Neurol. 13, 258--272 (][975).

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Fig. 3. (a) Mierofilaments (m/) distributed at random, at the periphery: "basal type material" (-->) (• 15840). (b)Microfilamentous bundle in a perivaseular sarcomatous element, (-->): "basal type material" (• 5400). (e) Myofibrils with primitive Z bands (• 15840)

There are distributed ~s follows: 10 rhabdomyos~rcom~s: O'Connell (1946), Koide (1957), Lopes d e F a r i a (1957), Legier and Wells (1967), Gala~ioto and Gaddoni: case number 2 (1971), Leedham (1972); Shnangshoti et al. (1973), Beekett quoted b y Shuangshoti, Min et al. (1975), personal ease.

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Table 1. Primary rhabdomyosareomas of the neuraxis with necropsy reports No.

Case authors

1

O'Connell (1946)

2

Lopes de Faria (1957)

3

Legier and Wells (1967)

4 5

Age (Year)

Sex

Site

F

Spinal cord (D10 -~ filum terminale)

F

Cerebellum (left hemisphere)

31/2

M

Cerebellmn (vermis)

Shuangshoti et al. (1968)

4

~[

Cerebellum (vermis) and 4th Ventricle

Galatioto and Gaddoni case 2 (1971) or Gullotta case 11 (1967)

31/2

F

Cerebellum (vermis)

51/2

52

6

Leedham (1972)

45

F

Cerebrum (right hemisphere)

7

Min et al. (1975)

48

M

Cerebrum (right hemisphere)

8

Present case

8

F

Pons, Bulb and Leptomeninges

2 "mesenchymomas" or mixed malignant mesenchymal tumors according to Rubinstein (1968 and 1972). 9 medullomyoblastomas: Marineseo and Goldstein (1933), Ziileh (1942), Boellard (1946), Ingraham and Bailey (1946), t~ussell and gubinstein (1959), Bofin and Ebels (1963), Misugi and Liss (1970), Lewis (1973), yon Gagel quoted by Ziileh. 1 gliomyosareoma (Goldman, 1969). 1 leiomyosarcoma (Galatioto and Gaddoni, case number 1, 1971). Some ease reports were not available : Del Rio i-Iortega mentioned by Galatioto and Gaddoni (1971), yon Gagel mentioned by Zfilch (1942), or not translated (Koide, 1957). Moreover Galatioto and Gaddoni (1971) and Gullotta (1967) refers to the same ease. There are only eight necropsy reports for tumors of a purely striated muscular nature (Table 1). The diffuse subarachnoidal spreading, the hydrocephalus and the quick lethal development (3 to 23 months) are common place. Visceral metastasis (liver) are only mentioned by Min et al. (1975). Considering its clinical, pathological and evolutive data, the rhabdomyosareoma is not very different from other tumors with muscular components (Fig. 4), but the few ease reports are of no statistical value and so lead to no conclusion. The highly exceptional character of those neoplasms accounts for the fact that they are not even mentioned in some treatises on neurooneology (Kernohan and Uihlein, 1962; Zfileh, 1971).

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Fig. 4. Localization of primary muscular tumors of the neuraxis

B. Histogenetic and IYosologic Comments According to gubinstein (1972, page 387) the nosological features of such tumors call for some clarification. There is, in fact, a problem of semantics which maintains some confusion in the matter. Some words refer clearly to the muscular componen~ either pure (rhabdomyosarcoma ; leiomyosarcoma) or in association (medullo and neuromyoblastoma, gliomyosarcoma). On the other hand, some terms are less precise or definite, involving the mesenchyme or embryonal tissue (embryonal sarcoma). So gubinstein just like Zfilch has a marked preference for the word " t e r a t o m a " , when there is a neuroepithelial component, rather than "medullomyoblastoma", introduced in 1933 by Marinesco and Goldstein. When there is no neuronal population ~ubinstein uses the word " m e s e n e h y m c m a " which, according to him, implies a rhabdomyoblastic and chondroblastic differentiation. Consequently those terms are used here with a meaning different from the one traditionally used for the same tumors in soft-tissues (Stout and Lattes, 1967). I n fact, as it is often the case with tumors, the vocabulary proceeds from histogenetic data based here essentially on dysembryoblastic theories. The oldest ones use the concept of " t e r a t o m a " which is different however from classical visceral teratomas (no ectodermal or endodermal derivatives). O'Connelrs case (1946) probably belongs to this group in view of the coexistence of a spina-bifida. Nichols and Wagner (1952) are of the opinion t h a t the origin should be looked for at the level of embryonic mesenchymal rests. Right now the participation of the ectomesenchyme of the neural crests seems the most possible, owing to the pathology and embryology. The works of Weed, Schaltenbrand and Bailey, Woollam and Millen (quoted b y Goldman, 1969) have proved t h a t the lophoneuroepithelium is the origin

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of t h e deep c o a t of t h e a r a c h n o i d , t h e p i a m a t e r , t h e t r a c t u s b e t w e e n t h e m , a n d t h e p e r i v a s c u l a r sheaths. T h e s c h a n n o g l i a which is a l o p h o n e u r o e p i t h e l i a l d e r i v a t i v e , is d i r e c t l y i n v o l v e d in t h e genesis of p e r i p h e r a l n e r v e r h a b d o m y o s a r c o m a s , which h a s b e e n o b s e r v e d b y P i e r r e Masson (1968) d u r i n g t h e y o n R e c k l i n g h a u s e n ' s n e u r o f i b r o m a t o s i s a n d confirmed b y o t h e r s ( W o o d r u f f et al., 1973). The ganglior h a b d o m y o s a r c o m a of t h e m e a t u s a c o u s t i c u s i n t e r n u s w i t h s u b a r a c h n o i d a l ext e n s i o n d e s c r i b e d b y H o l i m o n a n d R o s e n b l u m (1971) is also a p e r f e c t e x a m p l e of n e u r a l crest t u m o r s . I n o t h e r words, if t h e r e is no d o u b t t h a t t h e e c t o m e s e n c h y m e of n e u r a l crests p l a y e s a p a r t in t h e f o r m a t i o n of t u m o r s of t h e n e u r a x i s w i t h m u s c u l a r elements, t h e q u e s t i o n is to k n o w w h y this c h a r a c t e r i s t i c applies o n I y to some m e d u l l o b l a s t o m a s or to some glial or n e u r o n a l t u m o r s .

References Beckett, R. : Personal communication. Cit6 par Shuangshoti (1968) Boellard, J . W . : Ein Medulloblastom mit quergestreiften Muskelfasern. Arch. Psychiat. Nervenkr. 206, 228--236 (1964) Bofin, P. J., Ebels, E. : A case of medullomyoblastoma. Aeta neuropath. (Berl.) 2, 309--311 (1963) Cabanne, F., Tommasi, M., Michiels, R.: Les tumeurs de la r6gion pindale; revue g6n~rale bas@e sur dix observations personnelles. Ann. Anat. path. 10, 41--60 (1965) Galatioto, S., Gaddoni, G. : )s primitivi del SNC. Acta neurol. (Napoli) 26, 297--302 (1971) Goldman, R. L.: Gliomyosareoma of the cerebrum: report of a unique ease. Amer. J. clin. Path. ,52, 741--744 (1969) Gullotta, F. : ])as sogenannte Medulloblastom. Berlin-tIeidelberg-New York: Springer 1967 Holimon, J. L., Rosenblnm, W. L : Gangliorhabdomyosarcoma: a tumor of the ectomesenchyme. Case report. J. Neurosurg. 84, 417--422 (1971) Horn, R. C., Enterline, H. T.: Rhabdomyosarcoma: a clinico pathological study and classification of 39 eases. Cancer (Philad.) 11, 181--189 (1958) Ingraham, F. D., Bailey, O. T. : Cystic teratomas and teratoid tumors of the central nervous system in infancy and childhood. J. Neurosurg. 3, 511--532 (1946) Jellinker, D.: Primary intraeranial germ cell tumors. Acta neuropath. (Berl.) 25, 291--306 (1973) Kernohan, J. W., Uihlein, A.: Sarcomas of the brain. Springfield, Ill.: Ch. C. Thomas 1962 Koide, O. : A case of primary rhabdomyosarcoma of the brain. Gann 48, 645--647 (1957) Leedham, P. W.: Primary cerebral rhabdomyosarcoma and the problem of medullomyoblastoma. J. Neurol. Neurosurg. Psychiat. 4, 551--559 (1972) Legier, J. F., WelIs, It. A. : Primary cerebellar rhabdomyosarcoma. Case report. J. Neurosurg. 26, 436--438 (1967) Lewis, A. J.: Medulloblastoma with striated muscle fibers. Case report. J. Neurosurg. 38, 642--646 (1973) Lopes de Faria, J.: Rhabdomyosarcoma of the cerebellum. Arch. Path. 63, 234--238 (1957) Malamud, N. : Atlas of neuropathology. Berkeley-Los Angeles: University of California Press 1957 Marineseo, G., Goldstein,/r Sur une forme anatomique non encore d6crite de m6dulloblastome: m@dullomyoblastome. Ann. Anat. path. 10, 513--525 (1933) Marsden, H. B.: Cerebral rhabdomyosareoma. Arch. Dis. Child. 49, 498 (1974) Masson, J. K. : Embryonal rhabdomyosarcoma of the head and neck. Report on eighty eight cases. Amer. J. Surg. 110, 585--591 (1965) Masson, P.: Sarcomes rhabdopoi6tiques in Tumeurs humaines. (2@ @dit.) Paris: Maloine SA 1968 lVleyer, P. C., l%eah, T. G. : Secondary tumors of the central nervous system. Brit. J. Cancer 7, 43s (1953)

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Miller, R. W., Dalager, N. A. : Fatal rhabdomyosarcoma among children in the United States, 1960--1969. Cancer (Philad.) 34, 1897--1900 (1974) Min, K. W., Gyorkey, F., Halpert, B. : Primary rhabdomyosarcoma of the cerebrum. Cancer (Philad.) 5, 1405--1411 (1975) Misugi, K., Liss, L. : Medulloblastoma with cross-striated muscle. A fine structural study. Cancer (Philad.) 25, 1279--1285 (1970) Nichols, P., Wagner, J. A. : Primary intracranial sarcoma: report of 9 cases with suggested classification. J. Neuropath. exp. Neurol. l l , 215 (1952) O'Connell, J. E. A. : The subrachnoid dissemination of spinal tumours. J. Neurol. Neurosurg. Psychiat. 9, 55--62 (1946) Rio-ttortega ]:)el, A. P. : Neuroblastomas "Bol. Ac. Nac. Med.". Buenos Aires 1940; quoted by Galatioto and Gaddoni (1971) Rubinstein, L. J.: Sarcomas of the nervous system. In: Pathology of the nervous system. Vol. 2, (ed. J. Minekicr) New York: Mac-Graw Hill Book Company 1968 Rubinstein, L. J. : Tumors of the central nervous system in atlas of tumor pathology. Second series. Fascicle 6. Washington: Armed Forces Institute of Pathology 1972 Russel, D. S., Rubinstein, L. J. : Pathology of tumours of the nervous system. London: Arnold, LTD 12, 215--216 (1959) Shuangshoti, S., Piyaratn, P.,Viriyapanich, P. L. : Primary rhabdomyosarcoma of cerebellum. Necropsy report. Cancer (Philad.) 22, 367--371 (1968) Stout, A. P., Lattes, R. : Tumors of the soft tissues in atlas of tumor pathology. Second series. Fascicle 1. Washington: Armed forces Institute of Pathology 1967 Woodruff, J. M., Chernik, N. L., Smith, M. C. : Peripheral nerve tumors with rhabdomyosarcomatous differentiation (malignant Triton tumors). Cancer (Philad.) 32, 426--439 (1973) Ziilch, K. J. : Ein medulloblastom mit glatten Muskelfasern. Arch. Psychiat. Nervenkr. 114, 349--352 (1942) Zfilch, K. J. : Atlas of the histology of brain tumors. Berlin-Heidelberg-New York: Springer 1971 Dr. Basile Pasquier Laboratoire d'Anatomie-Pathologique C.~.U. de Grenoble 38700 La Tronche France