158 @ 1991 The Japanese Society of Pathology
Diffuse Malignant Peritoneal Mesothelioma in a Young Woman with a High Serum Level of CA125
Hui-Jun Duanl, Nobuo Itoh', Osamu Yamagami2, Tsutomu Katsuyama2, and Hidekazu Shigematsu'
An autopsy case of diffuse malignant peritoneal mesothelioma in a young woman who showed a high serum level of CA125 is reported. Autopsy revealed extensive tumor involvement of the visceral and parietal peritoneum. The liver, spleen and other abdominal viscera were encased by tumor nodules. Histologically, the polygonal tumor cells were arranged mostly i n a sheet-like fashion with a few tubular or papillary forms. No PAS reaction-positive mucin was recognized, but there was a strongly positive colloidal iron reaction. The colloidal iron positivity was effaced after combined treatment with hyaluronidase and sialidase. lmmunohistochemically the tumor cells showed strongly positive reactions for CA125, epithelial membrane antigen (EMA) and cytokeratin, weak positivity for carcinoembryonic antigen (CEA) and focal positivity for vimentin. Ultrastructurally, the most characteristic feature was the expression of numerous long microvilli projecting from the tumor cell surfaces and abundant long desmosomes between the tumor cells. We consider that pretreatment using a combination of hyaluronidase and sialidase might be useful for the diagnosis of malignant mesothelioma. CA125 staining should be performed routinely in cases where this tumor is suspected. Acta Pathol Jpn 41 : 158-163, 1991. Key words : Peritoneum, Mesothelioma, CA125
INTRODUCTION CA125 is known to be a useful tumor marker for gy necolog ica I cancers, especiaIly epit he1ia I ova ria n car-
cinomas. It has also been reported that some patients with non-gynecological cancers show elevated CA125 levels in serum, and that immunohistochemically, the Received July 31, 1990. Accepted for publication October 22, 1990. Department of 'Pathology and *CentralClinical Laboratories, Shinshu University School of Medicine, Matsumoto. Mailing address: Nobuo ltoh (@%aft), Department of Pathology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390, Japan.
tumor tissue is positive for CA125 (1, 2). We report here a case of diffuse malignant peritoneal mesothelioma in a young woman with a high serum level of CA125.
CASEREPORT A 15-year-old girl was admitted to the First Department of Medicine, Shinshu University Hospital, on June 24, 1982, with fever and increasingly severe abdominal pain. There was no history of asbestos exposure. On examination, tenderness was found in the right epigastrium. Abdominoscopy revealed intestinal adhesion as well as numerous small white nodules on the surface of the parietal peritoneum. This was interpreted as tuberculous peritonitis, and tuberculostatic drugs were administered, but no alleviation of the fever was observed. On December 4, 1982, minocycline was administered instead of tuberculostatics because of a finding of Pseudomonas cepacia. The fever was then relieved within a few days, and the patient was discharged from hospital on May 17, 1983. However on February 16, 1987, she was readmitted because of persistent abdominal pain since December 1986. Physical examination showed tenderness in the right hypogastrium. The relevant laboratory data were as follows: ESR 1 0 9 mm/h; Hb 8.9g/dl; WBC 5,900/mms; platelets 1 0 7 x 1 0 ' ; y-globulin 33.2%; serum C-reactive protein 6 + . Ascites was found on the echogram. Recurrence of tuberculous peritonitis was suspected. Despite administration of tuberculostatics and antibiotics, ascites gradually increased. The level of CA125 in the serum was found to be 11,270 U/ml on October 5, 1987. Gynecological examination revealed no abnormalities. A class lllb cytology of the ascites and a mild increase of hyaluronic acid in the ascites were reported on October 26, 1987. A clinical diagnosis of probable malignant peritoneal mesothelioma was made, and chemotherapy with mitomycin C was begun. Enlarged left supraclavicular
Acta Pathologica Japonica 41 (2) : 1991
lymph nodes were palpable, and a tumorous shadow of possible metastasis in the superior mediastinum was seen by chest X-ray examination in December 1987. Intestinal perforation developed on February 15, 1988, and the patient died on March 10, 1988. Permission for autopsy was obtained.
159
mm in diameter and a 4-mm perforation on the serous surface of the intestine were seen 3 0 c m distant from Treitz’s ligament. Two hundred milliliters of fluid was removed from the left pleural cavity. Many tiny seedlike tumor nodules were found under the visceral pleura of both lungs, and lymphangitis carcinomatosa was obvious on S9 of the left lung.
AUTOPSY FINDINGS Autopsy was performed 10 h after death. A nodule measuring 2 x 2 c m was seen in the superior mediastinum. The peritoneal cavity contained 5,000 ml of blood-tinged ascitic fluid, as well as numerous deposits of gray-white tumor tissue, which formed diffuse sheetlike thickenings, encasing and compressing the intestines, liver and spleen (Fig. 1). There were innumerable tumor nodules and plaques of various sizes on both the visceral and parietal peritoneal surfaces, but no primary area was identifiable. The tumor tissue had invaded the wall of the intestines and the parenchyma of the liver and spleen. The ovaries were normal in size, and no tumor tissue seen at their cut surfaces. An ulcer measuring 12
Microscopic findings The tumor tissues obtained at autopsy were fixed in phosphate-buffered formalin (pH 7.4), processed routine ly, and embedded in paraffin. Paraffin sections were stained with HE, PAS and colloidal iron with or without hyaluronidase and/or sialidase digestion. The tumor was of pure epithelial type. The tumor cells had round eccentric nuclei with a prominent nucleolus and relatively abundant eosinophilic cytoplasm. Mitotic activity was present, but was not prominent. The histological appearance varied in different areas. In some, round or polygonal cells arranged in solid sheets (Fig. 2a), occasionally surrounded the vessels. In others, gland-like or papillary tumors with cuboidal or flattened cells (Fig. 2b) were observed. Signet ring-like tumor cells were also seen in the invasive lesion of the liver. PAS-positive mucin was not recognized, but a colloidal iron-positive substance was present in the cytoplasm of the tumor cells and in the stromal tissue. After hyaluronidase or sialidase digestion, the stainability was still preserved, although weakened. However, the stainability became negative after combined hyaluronidase and sialidase pretreatment (Fig. 3).
Immunohistochemica I findings lmmunohistochemical staining was performed using the peroxidase-antiperoxidase method on paraffin sections. The immunological reagents employed included antibodies against CAI 25 (Oris, France), CEA (Milab, Sweden), EMA (Dakopatts, Denmark), cytokeratin (Becton Dickinson, CA, USA) and vimentin (Dakopatts). In spite of the different patterns of tumor cell arrangement, a large proportion of the tumor cells showed strongly positive reactions for CA125 (Fig. 4a), EMA and cytokeratin (Fig. 4b). Some of the tumor cells showed a weakly positive reaction for CEA. Vimentin was positively stained in the tumor cells showing a sheet-like arrangement, and was negative in those arranged in a gland-like pattern. Figurel. Photograph of tumor. The tumor nodules are becoming confluent. The loops of intestine are completely e n cased in the tumor.
Electron microsco pic findings For electron microscopy, parts of the tumor tissue
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Malignant Peritoneal Mesothelioma (Duan et a/.)
Figure 2. Light micrographs of tumor. The tumor cells were mostly arranged in solid sheets (a), but some were arranged in a gland-like pattern (b). HE.
obtained at autopsy were fixed in formalin and then transferred to 2.5% glutaraldehyde, post-fixed in 0smium tetroxide, dehydrated with an ethanol series, and embedded in Quetol 812. Ultrathin sections were cut and subjected to electron microscopic observation. There were numerous long bush-like microvilli on the tumor cell surfaces and abundant longer desmosomes between the tumor cells (Fig. 5).
DISCUSSION Autopsy of the present patient revealed diffuse tumor involvement in the abdominal cavity. From the typical gross (encasement of the intestines, liver and spleen), histochemical (negative PAS staining, presence of a colloidal iron-positive substance removed after hyaluronidase and sialidase digestion), immunohistochemical (weak staining for CEA and strong staining for cytokerat in) and ultrast ructural (long bush-li ke microv illi) f eatures, the diagnosis of diffuse malignant peritoneal mesot helioma was established. Diffuse malignant mesothelioma, particularly of the peritoneum, is rare in children (3). Most patients with mesothelioma die within one year following diagnosis
(4). The present patient was 15 years old at the onset of symptoms and survived for more than 5 years. It is also of interest that the patient showed a high serum level of CA125 and was immunohistochemically positive for CA125 in the tumor tissue. Kabawat et a l . ( 5 ) have shown that in fetal tissues CA125 reacts with derivatives of the coelomic epithelium, i. e. the mullerian epithelium, and the lining cells of the peritoneum, pleura and pericardium. Nouwen et a/. (6) have found that CA125 staining is positive in the adult pleural mesothelium, thus demonstrating that the expression of this antigen by the fetal coelomic epithelium continues into adulthood. Serum levels of CA125 have been reported to be high in serous surface carcinoma (7),which is thought to arise from the mesothelium (8). Koelma et a/. (2) reported that 25 of 11 1 non-gynecological malignant tumors derived from a variety of organs were positive for CA125, but that the only case of mesothelioma was negative. The high serum level and positive tumor cell reaction for CA125 in the present case further suggests that some tumors derived from the mesothelium still possess the capacity to secrete CA125. Therefore, CA125 staining is recommended in possible cases of this tumor.
Acta Pathologica Japonica 41 (2): 1991
161
Figure 3. Histochemical reactivity (colloidal iron preparations). a and d : A strongly positive colloidal iron reaction is present in the tumor cells. b and e : The reaction is still positive after digestion with only hyaluronidase, although it has become weaker. c and f : Combined digestion with hyaluronidase and sialidase has effaced the reaction. (a-c: cytology ; d-f section).
An immunoradiometric assay for detection of CA125 has been developed by Bast et a/. (1); using this method they found that the level of CA125 in serum was elevated in more than 80% of patients with ovarian cancer and 29% of patients with non-gynecological cancers, including carcinomas of the pancreas, stomach, colon and breast. However, the most remarkable elevations (above 1,500 U/ml; normal limit, 3 5 U/ml) were o b served in patients with epithelial ovarian cancer. Serum levels of CA125 should reflect both production and release of the antigen(6). In the present case, a very high CA125 level of 11,270 U/ml was present. Thus a high serum level of CA125 is rare even in ovarian cancers (1). The primary reason for the marked elevation of CA125 in this case may have been the large tumor volume as well as the extensive invasion and metastasis of tumor cells secreting large amounts of CA125. In addition, reduced hepatic clearance of CA125 as a result of tumor invasion to the liver may have been a factor, since elevated serum levels of CA125 in patients with benign chronic liver diseases have been considered to result from reduced hepatic clearance of CA125 (6). It is difficult to distinguish epithelial malignant mesothelioma from adenocarcinomas metastatic to the pleura
or peritoneum on the basis of histology alone. Histochemically, demonstration of neutral mucin, using PAS staining following diastase digestion, may help to exclude mesothelioma, whereas positive alcian blue or colloidal iron reactions removed by hyaluronidase sup port such a diagnosis. This is because neutral mucins are secreted by some adenocarcinomas, but not by mesotheliomas, whereas hyaluronic acid is produced by epithelial mesotheliomas but not by adenocarcinomas (9). However, some mesotheliomas still show slightly positive alcian blue or colloidal iron reactions after hyaluronidase digestion (lo), as seen in the present case. In view of a recent report that mesotheliomas secrete we tried to remove the colloidal ironsialic acid (1 l), positive substance with sialidase. Although the staining was weakened, it was still positive after digestion with sialidase alone, but became negative after combined digestion with hyaluronidase and sialidase. This finding further indicates that besides hyaluronic acid, some mesotheliomas also secrete sialic acid. Consequently, combined pretreatment with hya luronidase and sia lidase may be helpful for the diagnosis of diffuse malignant mesothelioma. Although histochemical methods have proven useful,
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Malignant Peritoneal Mesothelioma (Duan et a/.)
Figure 4. Immunostaining. Tumor cells stained for CA125 in the cell membrane (a); cytokeratin in cell membrane and cytoplasm (b). PAP-immunoperoxidase.
Figure 5. Electron micrograph showing long microvilli (length/width ratio2 15).
mosomes are also characteristic. ( x 30,000).
Longer des-
Acta Pathologica Japonica 41 (2): 1991
some mesotheliomas do not express the typical histochemical pattern. Many investigators have studied the usefulness of tumor markers as an aid to diagnosis (3, 10, 12-18). Wang et a/.(17) reported that CEA is present on adenocarcinoma cells, but not on mesothe lioma cells. However, some mesotheliomas can be positive for CEA (9, 10, 13). CEA was considered t o be useful for differential diagnosis between adenocarcinoma and mesothelioma by Loosli and Hurlimann (10), who found that CEA was present in all adenocarcinomas tested, whereas only 3 of 15 mesotheliomas were positive for CEA. Corson and Pinkus(13) showed that staining for CEA was more intense than that for cytokeratin in adenocarcinomas, whereas staining for cytokeratin was more intense than that f o r CEA in mesotheliomas. The weak staining for CEA and strong staining for cytokeratin in the present case supported the diagnosis. Ultrast ruct ura Ily, mesothe1iomas share some similarities with adenocarcinomas, but the length/width ratio (L/W) of microvilli is a useful parameter for defining mesotheliomas (19, 20). No adenocarcinoma has L/W greater than 10 (19) and a mean L/W of more than 11 supports a diagnosis of mesothelioma (20). In the present case, microvilli with a L/W greater than 10 were often observed. Serous surface carcinoma of the peritoneum, also thought to arise from the mesothelium, must also be differentiated from malignant mesothelioma (7,8). The present case differed from serous surface carcinoma of the peritoneum in the following features: absence of psammoma bodies ; presence of hyaluronic acid and absence of neutral mucin in tumor cells; deep invasion into abdominal organs (liver and spleen) ; distant metastasis. Acknow/&gements : We are grateful to Miss T. Nishizawa, Miss N. Aoshima and Mrs M. Watanabe for technical assistance.
REFERENCES Bast RC, Klug TL, John ES, et a/. A radioimmunoassay using a monoclonal antibody to monitor the course of epithelial ovarian cancer. N Engl J Med 309: 883887, 1983. Koelma IA, Nap M, Rodenburg CJ, and Fleuren GJ. The value of tumour marker CA125 in surgical pathology. Histopathology 11: 287-294, 1987. Talerman A, Chilcote RR, Montero JR, and Okagaki T. Diffuse malignant peritoneal mesothelioma in a 13year-old girl. Report of a case and review of the literature. Am J Surg Pathol 9 : 73-80, 1985. Kannerstein M and Churg J. Peritoneal mesothelioma.
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Hum Pathol 8: 83-94, 1977. 5. Kabawat SE, Bast RC, Bhan AK, et a/. Tissue distribution of a coelomic epithelium-related antigen recognized by the monoclonal antibody OC125. Int J Gynecol Pathol 2: 257-285, 1983. 6. Nouwen EJ, Pollet DE, Eerdekens MW, et a/. Immunohistochemical localization of placental alkaline phosphatase, carcinoembryonic antigen, and cancer antigen 125 in normal and neoplastic human lung. Cancer Res 46 : 866-876, 1986. 7. Mills SE, Anderson WA, Fechner RE, and Austin MB. Serous surface papillary carcinoma. A clinicopathologic study of 10 cases and comparison with stage 111IV ovarian serous carcinoma. Am J Surg Pathol 12 : 827-834, 1988. 8. Truong LD, Maccato ML, Awalt H, et a/. Serous surface carcinoma of the peritoneum : A clinicopathologic study of 22 cases. Hum Pathol 21 : 99-110, 1990. 9. Roggli VL, Kolbeck J, Sanfilippo F, and Shelburne JD. Pathology of human mesothelioma : Etiologic and diagnostic consideration. Pathol Annu 22 (Part 2) : 91-131, 1987. 10. Loosli H and Hurlimann J. lmmunohistological study of malignant diffuse mesotheliomas of the pleura. Histopathology 8: 793-803, 1984. 11. Kawai T. Difference of heteropolysaccharide in malignant pleural mesothelioma and adenocarcinoma of the lung. lgaku no Ayumi 147 : 681, 1988 (in Japanese). 12. Churg A. lmmunohistochemical staining for vimentin and keratin in malignant mesothelioma. Am J Surg Pathol 9 : 360-365, 1985. 13. Corson JM and Pinkus GS. Mesothelioma : Profile of keratin proteins and carcinoembryonic antigen. An immunoperoxidase study of 20 cases and comparison with pulmonary adenocarcinomas. Am J Pathol 108: 80-87, 1982. 14. Sheibani K, Battifora H, Burke JS, and Rappaport H. Leu M1 antigen in human neoplasms: An immunohistologic study of 400cases. Am J Surg Pathol 10: 227-236, 1986. 15. Strickler JG, Herndier BG, and Rouse RV. Immunohistochemical staining in malignant mesotheliomas. Am J Clin Pathol 86: 610-614, 1987. 16. Szpak CA, Johnston WW, Roggli V. et a/. The diagnostic distinction between malignant mesothelioma of the pleura and adenocarcinoma of the lung as defined by a monoclonal antibody (872. 3). Am J Pathol 122: 252-260, 1986. 17. Wang NS, Huang SN, and Gold P. Absence of carcinoembryonic antigen-like material in mesothelioma. Cancer 44 : 937-943, 1979. 18. Warnock M, Stoloff A, and Thor A. Differentiation of adenocarcinoma of the lung from mesothelioma. Periodic acid-schiff, monoclonal antibodies 872. 3. and Leu M1. Am J Pathol 133: 30-38, 1988. 19. Warhol MJ, Hickey WF, and Corson JM. Malignant mesothelioma. Ultrastructural distinction from adenocarcinoma. Am J Surg Pathol 6 : 307-314, 1982. 20. Burns TR, Greenberg SD, Mace ML, and Johnson EH. Ultrastructural diagnosis of epithelial malignant mesothelioma. Cancer 56 : 2036-2040, 1985.
Diffuse Malignant Peritoneal Mesothelioma in a Young Woman with a High Serum Level of CA125
Hui-Jun Duanl, Nobuo Itoh', Osamu Yamagami2, Tsutomu Katsuyama2, and Hidekazu Shigematsu'
An autopsy case of diffuse malignant peritoneal mesothelioma in a young woman who showed a high serum level of CA125 is reported. Autopsy revealed extensive tumor involvement of the visceral and parietal peritoneum. The liver, spleen and other abdominal viscera were encased by tumor nodules. Histologically, the polygonal tumor cells were arranged mostly i n a sheet-like fashion with a few tubular or papillary forms. No PAS reaction-positive mucin was recognized, but there was a strongly positive colloidal iron reaction. The colloidal iron positivity was effaced after combined treatment with hyaluronidase and sialidase. lmmunohistochemically the tumor cells showed strongly positive reactions for CA125, epithelial membrane antigen (EMA) and cytokeratin, weak positivity for carcinoembryonic antigen (CEA) and focal positivity for vimentin. Ultrastructurally, the most characteristic feature was the expression of numerous long microvilli projecting from the tumor cell surfaces and abundant long desmosomes between the tumor cells. We consider that pretreatment using a combination of hyaluronidase and sialidase might be useful for the diagnosis of malignant mesothelioma. CA125 staining should be performed routinely in cases where this tumor is suspected. Acta Pathol Jpn 41 : 158-163, 1991. Key words : Peritoneum, Mesothelioma, CA125
INTRODUCTION CA125 is known to be a useful tumor marker for gy necolog ica I cancers, especiaIly epit he1ia I ova ria n car-
cinomas. It has also been reported that some patients with non-gynecological cancers show elevated CA125 levels in serum, and that immunohistochemically, the Received July 31, 1990. Accepted for publication October 22, 1990. Department of 'Pathology and *CentralClinical Laboratories, Shinshu University School of Medicine, Matsumoto. Mailing address: Nobuo ltoh (@%aft), Department of Pathology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto 390, Japan.
tumor tissue is positive for CA125 (1, 2). We report here a case of diffuse malignant peritoneal mesothelioma in a young woman with a high serum level of CA125.
CASEREPORT A 15-year-old girl was admitted to the First Department of Medicine, Shinshu University Hospital, on June 24, 1982, with fever and increasingly severe abdominal pain. There was no history of asbestos exposure. On examination, tenderness was found in the right epigastrium. Abdominoscopy revealed intestinal adhesion as well as numerous small white nodules on the surface of the parietal peritoneum. This was interpreted as tuberculous peritonitis, and tuberculostatic drugs were administered, but no alleviation of the fever was observed. On December 4, 1982, minocycline was administered instead of tuberculostatics because of a finding of Pseudomonas cepacia. The fever was then relieved within a few days, and the patient was discharged from hospital on May 17, 1983. However on February 16, 1987, she was readmitted because of persistent abdominal pain since December 1986. Physical examination showed tenderness in the right hypogastrium. The relevant laboratory data were as follows: ESR 1 0 9 mm/h; Hb 8.9g/dl; WBC 5,900/mms; platelets 1 0 7 x 1 0 ' ; y-globulin 33.2%; serum C-reactive protein 6 + . Ascites was found on the echogram. Recurrence of tuberculous peritonitis was suspected. Despite administration of tuberculostatics and antibiotics, ascites gradually increased. The level of CA125 in the serum was found to be 11,270 U/ml on October 5, 1987. Gynecological examination revealed no abnormalities. A class lllb cytology of the ascites and a mild increase of hyaluronic acid in the ascites were reported on October 26, 1987. A clinical diagnosis of probable malignant peritoneal mesothelioma was made, and chemotherapy with mitomycin C was begun. Enlarged left supraclavicular
Acta Pathologica Japonica 41 (2) : 1991
lymph nodes were palpable, and a tumorous shadow of possible metastasis in the superior mediastinum was seen by chest X-ray examination in December 1987. Intestinal perforation developed on February 15, 1988, and the patient died on March 10, 1988. Permission for autopsy was obtained.
159
mm in diameter and a 4-mm perforation on the serous surface of the intestine were seen 3 0 c m distant from Treitz’s ligament. Two hundred milliliters of fluid was removed from the left pleural cavity. Many tiny seedlike tumor nodules were found under the visceral pleura of both lungs, and lymphangitis carcinomatosa was obvious on S9 of the left lung.
AUTOPSY FINDINGS Autopsy was performed 10 h after death. A nodule measuring 2 x 2 c m was seen in the superior mediastinum. The peritoneal cavity contained 5,000 ml of blood-tinged ascitic fluid, as well as numerous deposits of gray-white tumor tissue, which formed diffuse sheetlike thickenings, encasing and compressing the intestines, liver and spleen (Fig. 1). There were innumerable tumor nodules and plaques of various sizes on both the visceral and parietal peritoneal surfaces, but no primary area was identifiable. The tumor tissue had invaded the wall of the intestines and the parenchyma of the liver and spleen. The ovaries were normal in size, and no tumor tissue seen at their cut surfaces. An ulcer measuring 12
Microscopic findings The tumor tissues obtained at autopsy were fixed in phosphate-buffered formalin (pH 7.4), processed routine ly, and embedded in paraffin. Paraffin sections were stained with HE, PAS and colloidal iron with or without hyaluronidase and/or sialidase digestion. The tumor was of pure epithelial type. The tumor cells had round eccentric nuclei with a prominent nucleolus and relatively abundant eosinophilic cytoplasm. Mitotic activity was present, but was not prominent. The histological appearance varied in different areas. In some, round or polygonal cells arranged in solid sheets (Fig. 2a), occasionally surrounded the vessels. In others, gland-like or papillary tumors with cuboidal or flattened cells (Fig. 2b) were observed. Signet ring-like tumor cells were also seen in the invasive lesion of the liver. PAS-positive mucin was not recognized, but a colloidal iron-positive substance was present in the cytoplasm of the tumor cells and in the stromal tissue. After hyaluronidase or sialidase digestion, the stainability was still preserved, although weakened. However, the stainability became negative after combined hyaluronidase and sialidase pretreatment (Fig. 3).
Immunohistochemica I findings lmmunohistochemical staining was performed using the peroxidase-antiperoxidase method on paraffin sections. The immunological reagents employed included antibodies against CAI 25 (Oris, France), CEA (Milab, Sweden), EMA (Dakopatts, Denmark), cytokeratin (Becton Dickinson, CA, USA) and vimentin (Dakopatts). In spite of the different patterns of tumor cell arrangement, a large proportion of the tumor cells showed strongly positive reactions for CA125 (Fig. 4a), EMA and cytokeratin (Fig. 4b). Some of the tumor cells showed a weakly positive reaction for CEA. Vimentin was positively stained in the tumor cells showing a sheet-like arrangement, and was negative in those arranged in a gland-like pattern. Figurel. Photograph of tumor. The tumor nodules are becoming confluent. The loops of intestine are completely e n cased in the tumor.
Electron microsco pic findings For electron microscopy, parts of the tumor tissue
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Malignant Peritoneal Mesothelioma (Duan et a/.)
Figure 2. Light micrographs of tumor. The tumor cells were mostly arranged in solid sheets (a), but some were arranged in a gland-like pattern (b). HE.
obtained at autopsy were fixed in formalin and then transferred to 2.5% glutaraldehyde, post-fixed in 0smium tetroxide, dehydrated with an ethanol series, and embedded in Quetol 812. Ultrathin sections were cut and subjected to electron microscopic observation. There were numerous long bush-like microvilli on the tumor cell surfaces and abundant longer desmosomes between the tumor cells (Fig. 5).
DISCUSSION Autopsy of the present patient revealed diffuse tumor involvement in the abdominal cavity. From the typical gross (encasement of the intestines, liver and spleen), histochemical (negative PAS staining, presence of a colloidal iron-positive substance removed after hyaluronidase and sialidase digestion), immunohistochemical (weak staining for CEA and strong staining for cytokerat in) and ultrast ructural (long bush-li ke microv illi) f eatures, the diagnosis of diffuse malignant peritoneal mesot helioma was established. Diffuse malignant mesothelioma, particularly of the peritoneum, is rare in children (3). Most patients with mesothelioma die within one year following diagnosis
(4). The present patient was 15 years old at the onset of symptoms and survived for more than 5 years. It is also of interest that the patient showed a high serum level of CA125 and was immunohistochemically positive for CA125 in the tumor tissue. Kabawat et a l . ( 5 ) have shown that in fetal tissues CA125 reacts with derivatives of the coelomic epithelium, i. e. the mullerian epithelium, and the lining cells of the peritoneum, pleura and pericardium. Nouwen et a/. (6) have found that CA125 staining is positive in the adult pleural mesothelium, thus demonstrating that the expression of this antigen by the fetal coelomic epithelium continues into adulthood. Serum levels of CA125 have been reported to be high in serous surface carcinoma (7),which is thought to arise from the mesothelium (8). Koelma et a/. (2) reported that 25 of 11 1 non-gynecological malignant tumors derived from a variety of organs were positive for CA125, but that the only case of mesothelioma was negative. The high serum level and positive tumor cell reaction for CA125 in the present case further suggests that some tumors derived from the mesothelium still possess the capacity to secrete CA125. Therefore, CA125 staining is recommended in possible cases of this tumor.
Acta Pathologica Japonica 41 (2): 1991
161
Figure 3. Histochemical reactivity (colloidal iron preparations). a and d : A strongly positive colloidal iron reaction is present in the tumor cells. b and e : The reaction is still positive after digestion with only hyaluronidase, although it has become weaker. c and f : Combined digestion with hyaluronidase and sialidase has effaced the reaction. (a-c: cytology ; d-f section).
An immunoradiometric assay for detection of CA125 has been developed by Bast et a/. (1); using this method they found that the level of CA125 in serum was elevated in more than 80% of patients with ovarian cancer and 29% of patients with non-gynecological cancers, including carcinomas of the pancreas, stomach, colon and breast. However, the most remarkable elevations (above 1,500 U/ml; normal limit, 3 5 U/ml) were o b served in patients with epithelial ovarian cancer. Serum levels of CA125 should reflect both production and release of the antigen(6). In the present case, a very high CA125 level of 11,270 U/ml was present. Thus a high serum level of CA125 is rare even in ovarian cancers (1). The primary reason for the marked elevation of CA125 in this case may have been the large tumor volume as well as the extensive invasion and metastasis of tumor cells secreting large amounts of CA125. In addition, reduced hepatic clearance of CA125 as a result of tumor invasion to the liver may have been a factor, since elevated serum levels of CA125 in patients with benign chronic liver diseases have been considered to result from reduced hepatic clearance of CA125 (6). It is difficult to distinguish epithelial malignant mesothelioma from adenocarcinomas metastatic to the pleura
or peritoneum on the basis of histology alone. Histochemically, demonstration of neutral mucin, using PAS staining following diastase digestion, may help to exclude mesothelioma, whereas positive alcian blue or colloidal iron reactions removed by hyaluronidase sup port such a diagnosis. This is because neutral mucins are secreted by some adenocarcinomas, but not by mesotheliomas, whereas hyaluronic acid is produced by epithelial mesotheliomas but not by adenocarcinomas (9). However, some mesotheliomas still show slightly positive alcian blue or colloidal iron reactions after hyaluronidase digestion (lo), as seen in the present case. In view of a recent report that mesotheliomas secrete we tried to remove the colloidal ironsialic acid (1 l), positive substance with sialidase. Although the staining was weakened, it was still positive after digestion with sialidase alone, but became negative after combined digestion with hyaluronidase and sialidase. This finding further indicates that besides hyaluronic acid, some mesotheliomas also secrete sialic acid. Consequently, combined pretreatment with hya luronidase and sia lidase may be helpful for the diagnosis of diffuse malignant mesothelioma. Although histochemical methods have proven useful,
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Malignant Peritoneal Mesothelioma (Duan et a/.)
Figure 4. Immunostaining. Tumor cells stained for CA125 in the cell membrane (a); cytokeratin in cell membrane and cytoplasm (b). PAP-immunoperoxidase.
Figure 5. Electron micrograph showing long microvilli (length/width ratio2 15).
mosomes are also characteristic. ( x 30,000).
Longer des-
Acta Pathologica Japonica 41 (2): 1991
some mesotheliomas do not express the typical histochemical pattern. Many investigators have studied the usefulness of tumor markers as an aid to diagnosis (3, 10, 12-18). Wang et a/.(17) reported that CEA is present on adenocarcinoma cells, but not on mesothe lioma cells. However, some mesotheliomas can be positive for CEA (9, 10, 13). CEA was considered t o be useful for differential diagnosis between adenocarcinoma and mesothelioma by Loosli and Hurlimann (10), who found that CEA was present in all adenocarcinomas tested, whereas only 3 of 15 mesotheliomas were positive for CEA. Corson and Pinkus(13) showed that staining for CEA was more intense than that for cytokeratin in adenocarcinomas, whereas staining for cytokeratin was more intense than that f o r CEA in mesotheliomas. The weak staining for CEA and strong staining for cytokeratin in the present case supported the diagnosis. Ultrast ruct ura Ily, mesothe1iomas share some similarities with adenocarcinomas, but the length/width ratio (L/W) of microvilli is a useful parameter for defining mesotheliomas (19, 20). No adenocarcinoma has L/W greater than 10 (19) and a mean L/W of more than 11 supports a diagnosis of mesothelioma (20). In the present case, microvilli with a L/W greater than 10 were often observed. Serous surface carcinoma of the peritoneum, also thought to arise from the mesothelium, must also be differentiated from malignant mesothelioma (7,8). The present case differed from serous surface carcinoma of the peritoneum in the following features: absence of psammoma bodies ; presence of hyaluronic acid and absence of neutral mucin in tumor cells; deep invasion into abdominal organs (liver and spleen) ; distant metastasis. Acknow/&gements : We are grateful to Miss T. Nishizawa, Miss N. Aoshima and Mrs M. Watanabe for technical assistance.
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