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Malignant hemangiopericytoma of the omentum presenting as an ovarian tumor
GYNECOLOGlC
ONCOLOGY
39, 208-213
(1990)
CASE REPORT Malignant Hemangiopericytoma of the Omentum Presenting as an Ovarian Tumor MASASHI IMACHI, M.D., NAOKI TSUKAMOTO, M.D., KIYOMI TSUKIMORI, HITOO
NAKANO,
M.D.,
TOSHIYUKI
SHIGEMATSU,
M.D.,*
M.D., KUNIAKI FUNAKOSHI, M.D., TANIMURA, M.D.t
AND AKIRA
Department of Gynecology and Obstetrics, Kyushu University Faculty of Medicine, Maidashi 3-l-1, Higashi-ku, Fukuoka 812; and *Department of Obstetrics and Gynecology and TDepartment of Pathology, Shimonoseki Municipal Central Hospital, Koyocho l-13-1, Shimonoseki 750, Japan Received
March
Malignant hemangiopericytomas are usually found in the musculature of the extremities, the retroperitoneum, and the pelvis. Malignant hemangiopericytoma arising in the omentum is extremely rare. We recently experienced such a case, in which a malignant ovarian tumor was suspected preoperatively on the basis of the sonogram, CT scan, magnetic resonance image, and increased CA-125 value. Microscopically, the tumor showed many mitoses, increased cellularity, and cytologic atypia. The patient was treated with CAP combination therapy following resection of the tumor; however, an intraperitoneal recurrence probably due to implantation was recognized 11 months later. Q 1990 academic Press, Inc.
INTRODUCTION Hemangiopericytoma was first described by Stout and Murray in 1942 [I]. It is an uncommon tumor arising
from the pericytes. This tumor may occur at any site where capillaries are found [2,3]; however, malignant hemangiopericytoma of the omentum is extremely rare. Only three well-documented cases have been previously reported in the English literature [4-71. We now report the fourth case of this tumor, the first in a woman. CASE REPORT A 62-year-old Japanese woman, gravida 4, para 3, was admitted to Shimonoseki Municipal Central Hospital with complaints of abdominal distension and pain on August 10, 1988. Her past medical history was noncontributory. Seven months prior to admission, the patient noticed increasing abdominal girth, diarrhea, and weight loss. 208 0090-8258&O$1.50 Copyright 0 1990 by Academic Press, Inc. All rights of reproduction in any form reserved.
1. 1990
Physical examination revealed a distended abdomen with a huge cystic abdominopelvic mass reaching two fingerbreadths above the navel. Pelvic examination revealed a normal external genitalia, vagina, and cervix. The uterine body was not clearly palpable due to a large abdominopelvic mass. Pelvic sonogram, CT scan, and magnetic resonance imaging showed a multilocular cyst with some solid parts and moderate ascites (Fig. 1). Laboratory tests revealed mild anemia (Hb 9.6 g/dl), a high level of LDH (738 U/liter), C-reative protein of 6.8 mg/dl, and CA-125 of 1300 U/ml. Chest X rays, intravenous pyelogram, barium enema, cystoscopy, and sigmoidoscopy were within normal limits. A malignant ovarian tumor was suspected and the patient underwent a laparotomy on August 17, 1988. About 2000 ml of yellowish ascites was present. A large cystic tumor arising from the omentum was detected (Fig. 2). Frozen-section diagnosis of this tumor was reported as leiomyosarcoma. The uterus and bilateral ovaries were grossly normal. Exploration of the abdominal cavity revealed no intraperitoneal spread. The patient underwent total omentectomy, simple hysterectomy, bilateral salpingo-oophorectomy, and biopsy of paraaortic lymph nodes. Complete resection of the tumor was performed. Cytology of ascites was negative. Final pathological diagnosis was reported as malignant hemangiopericytoma arising and localized in the omentum. Postoperatively, the patient was given ten courses of adjuvant combination chemotherapy consisting of cyclophosphamide 400 mg/m2, Adriamycin 40 mg/m2, and c&platinum 40 mg/m2 (CAP) every 4 weeks. LDH and CA-125 returned to normal and remained normal. The patient showed no
209
CASE REPORT
FIG. 1. Sagittal magnetic resonance image showing a huge multilocular cyst with some solid parts and moderate ascites. M, mass; uterus.
evidence of disease on physical examination until June 1989. However, sonogram and CT scan revealed an intraabdominal mass in July 1989 and a second laparotomy was performed on July 19, 1989. Several intraperitoneal polypoid tumors growing from the parietal peritoneum and the mesentery were recognized. PATHOLOGICAL FINDINGS Grossly, the tumor was dark and lobulated, measured 24 x 20 x 12 cm, and weighed 2400 g. It was connected to the omentum via a pedicle with some dilated vessels. The capsule had already been partly ruptured. The cut surface revealed a variegated appearance with gray-tan, gray-yellowish, and multiple hemorrhagic and/or necrotic areas. Microscopically, round or spindle-shaped tumor cells were packed around the developed vascular channels and numerous capillaries. The vessels were thin walled and lined by a single layer of flattened nonneoplastic endothelial cells (Fig. 3). Cellularity was high and nuclear atypia was moderate to severe. Many mitotic figures
U,
(12/10 HPF) were also observed (Fig. 4). The reticulin stain revealed well-developed reticular meshworks and tumor cells outside the vascular spaces (Fig. 5). The tumor cells were positive by immunocytochemical stains for vimentin, and negative for S-100 protein, myoglobin, desmin, actin, and factor VIII. Electron microscopic examination was also performed. Tumor cells showed no specific findings. The nuclei were ovoid or spindle-shaped and contained a prominent single nucleolus. The cytoplasm was scanty and mitochondria, rough endoplasmic reticulum, free ribosomes, and Golgi apparatus were present. Tumor cells were surrounded by basal lamina and separated from endothelial cells by the basement membranes; however, there were no features by which tumor cells could be differentiated from smooth muscle cells. DISCUSSION Hemangiopericytoma is a vascular tumor that arises from the pericytes surrounding the capillaries [l-3]. These tumors are uncommon, and half of them are re-
IMACHI ET AL.
FIG. 2. Large cystic tumor of the omentum and normal internal genitalia.
ported as malignant. They are most commonly found in the musculature of the lower extremities, retroperitoneum, and pelvis [2]. Malignant hemangiopericytoma arising in the omentum is extremely rare and only three well-documented cases have been reported [4-61. If we apply the criteria for uterine sarcomas [8,9], the tumor in our patient may be histologically malignant according to the findings of numerous mitoses, increased cellularity, and cytologic atypia. However, there are no definite morphological criteria on which to differentiate malignant hemangiopericytoma from benign hemangiopericytoma [3,10-121. Binder et al. [13] reported that criteria such as anaplastic nuclear changes and mitoses are not reliable for the diagnosis of malignant hemangiopericytoma. On the other hand, the number of mitotic figures, increased cellularity, presence of cellular anaplasia, and foci of hemorrhage and necrosis can help distinguish the tumors as benign or malignant [2,14]. McMaster et al. [15] classified 60 patients with he-
mangiopericytoma histologically as benign, borderline malignant, and malignant on the basis of microscopic findings such as vascular pattern, shape of pericytes, anaplasia of pericytes, number of mitotic figures, and reticulin pattern. They reported that the 16 patients with borderline malignant tumors and the 32 patients with malignant tumors had a greater degree of cellular anaplasia and a larger number of mitotic figures than the 12 patients with benign tumors. In our case, all these findings (numerous mitotic figures, cellular anaplasia, and increased cellularity) were observed. The histological features of hemangiopericytoma resemble those of hemangioendothelioma, glomus tumor, leiomyosarcoma, synovial sarcoma, chondrosarcoma, mesothelioma, liposarcoma, and malignant fibrous histiocytoma [2]. In our case, the intraoperative diagnosis by frozen section was leiomyosarcoma; however, negative immunocytochemical stains for desmin and the lack of features differentiating smooth muscle cells by elec-
CASE REPORT
211
FIG. 3. Low-power photomicrograph of the tumor showing round or spindle-shaped tumor cells around developed vascular channels and capillaries. H&E, x 40.
tron microscopic study ruled out the diagnosis of leiomyosarcoma. The incidence of recurrence and/or metastasis of malignant hemangiopericytoma is difticult to predict. Enzinger er al. [2,16] reported that the incidence of metastases varied from 12 to 56% and local recurrences preceded metastases in more than two-thirds of the patients with evidence of metastatic disease. The IO-year survival rate was 70% by Enzinger and Smith [2]. Longterm follow-up is recommended because metastases may become apparent in patients after 5 or more disease-free years [ 15,171. In particular, intraabdominal hemangiopericytomas excluding those of uterine and gastric origin are frequently malignant [13]. Metastases usually occur by the hematogenous route and lymph node metastases are rare [15]. In our patient, intraabdominal recurrence probably due to implantation was observed 11 months later; however, no distant metastasis was found. The
detailed diagnosis of the omental tumor is often made with angiography [6,18]. However, the preoperative diagnosis of malignant hemangiopericytoma of the omenturn is very difficult. In our patient, a malignant ovarian tumor was suspected preoperatively by the findings of sonogram, CT scan, magnetic resonance imaging, and a high CA-125 value. The primary therapy of this tumor should be surgical [13,15]. In our patient, total omentectomy, simple hysterectomy, bilateral salpingo-oophorectomy, and biopsy of paraaortic lymph nodes were performed. The role of chemotherapy for this tumor is not established [13]. Some have reported the efficacy of Adriamycin for malignant hemangiopericytoma [ 19-211. Our patient was treated with CAP combination chemotherapy, but the tumor recurred within 11 months. The effectiveness of radiation therapy for this tumor has not been established n31.
212
IMACHI ET AL.
FIG. 4. High-power photomicrograph of the tumor showing cytologic atypia, numerous mitoses, and increased cellularity. H&E, x 400.
REFERENCES 1. Stout, A. P., and Murray, M. P. Hemangiopericytoma: A vascular tumor featuring Zimmerman’s pericytes, Ann. Surg. 116, 26-33 (1942). 2. Enzinger, F. M., and Smith, B. H. Hemangiopericytoma: An analysis of 106 cases, Hum. Pahol. 7, 61-82 (1976). 3. Stout, A. P. Hemangiopericytoma: A study of 25 new cases, Cancer 2, 1027-1054 (1949). 4. Stout, A. P., Hendry, J., and Purdie, F. J. Primary solid tumors of the great omentum, Cancer 16, 231-243 (1963). 5. Harder, V. T., Koischwitz, D., and Engel, C. Primary tumors of the mesentery and great omentum, Forts&r. Rontgenstr. 139,274280 (1983). 6. Iijima, T., Kon, Y., Zuguchi, M., Hatakeyama, M., Takahashi, K., Heshiki, A., Ogata, N., and Harada, T. Radiological diagnosis of the omental masses, Japan. J. Clin. Radial. 28,611-614 (1983). 7. Goldberger, R. E., and Schein, C. J. Hemangiopericytoma of the omentum. Report of a case with an unique presentation and review of the literature, Amer. Surg. 34, 291-295 (1968). 8. Norris, H. J., and Taylor, H. B. Mesenchymal tumors of the uterus, Cancer 19, 755-766 (1%6).
9. Kempson, R. L., and Bari, W. Uterine sarcoma: Classification, diagnosis and prognosis, Hum. Puthol. 1, 331-349 (1970). 10. Stout, A. P. Tumors featuring pericytes, Lab. Invest. 5, 217-223 (1956). 11. Kauffman, S. L., and Stout, A. P. Hemangiopericytoma in children, Cancer 13, 695-710 (1960). 12. Kauffman, S. L., and Stout, A. P. Congenital mesenchymal tumors, Cancer 18, 460-476 (1965). 13. Binder S. C., Wolfe, H. J., and Deterling, R. A. Intra-abdominal hemangiopericytoma, Arch. Surg. 107, 536-543 (1973). 14. Hacken, J. B., and Athey, P. A. Recurrent and metastatic retroperitoneal hemangiopericytoma, J. Comput. Tomogr. 9, 257-259 (1985). 15. McMaster, M. J., Soule, E. H., and Ivins, J. C. Hemangiopericytoma: A clinicopathologic study and long-term follow-up of 60 patients, Cancer 36, 2232-2244 (1975). 16. Enzinger, F. M., and Weiss, S. W. Hemangiopericytoma, in Soft tissue tumors, Mosby, St. Louis, pp. 463-481 (1983). 17. Backwindel, K. D., and Diddams, J. A. Hemangiopericytoma. Report of a case and comprehensive review of the literature, Cancer 25, 896-901 (1970).
CASE REPORT
213
PIG. 5. Reticulin stain showing a developed reticular meshwork and tumor cells outside the vascular spaces. x 100.
18. Fataar, S., Morton, P. C. G., Schulman, A., Roman, T., and Harvey, A. Radiological diagnosis of primary greater omental mass lesions, Clin. Radiol. 32, 325-330 (1981). 19. Wong, P. P., and Yagoda, A. Chemotherapy of malignant hemangiopericytoma, Cancer 41, 1256-1260 (1978).
20. Morris, D. M., Vuthiganon, C., Chang, P., Wiemnik, P. H., and Elias, E. G. Adriamycin in management of malignant hemangiopericytoma, Amer. Surg. 47, 441-446 (1981). 21. Beadle, G. F., and Hillcoat, B. L. Treatment of advanced malignant hemangiopericytoma with combination adriamycin and DTIC: A report of four cases, .I. Surg. Oncol. 22, 167-170 (1983).
ONCOLOGY
39, 208-213
(1990)
CASE REPORT Malignant Hemangiopericytoma of the Omentum Presenting as an Ovarian Tumor MASASHI IMACHI, M.D., NAOKI TSUKAMOTO, M.D., KIYOMI TSUKIMORI, HITOO
NAKANO,
M.D.,
TOSHIYUKI
SHIGEMATSU,
M.D.,*
M.D., KUNIAKI FUNAKOSHI, M.D., TANIMURA, M.D.t
AND AKIRA
Department of Gynecology and Obstetrics, Kyushu University Faculty of Medicine, Maidashi 3-l-1, Higashi-ku, Fukuoka 812; and *Department of Obstetrics and Gynecology and TDepartment of Pathology, Shimonoseki Municipal Central Hospital, Koyocho l-13-1, Shimonoseki 750, Japan Received
March
Malignant hemangiopericytomas are usually found in the musculature of the extremities, the retroperitoneum, and the pelvis. Malignant hemangiopericytoma arising in the omentum is extremely rare. We recently experienced such a case, in which a malignant ovarian tumor was suspected preoperatively on the basis of the sonogram, CT scan, magnetic resonance image, and increased CA-125 value. Microscopically, the tumor showed many mitoses, increased cellularity, and cytologic atypia. The patient was treated with CAP combination therapy following resection of the tumor; however, an intraperitoneal recurrence probably due to implantation was recognized 11 months later. Q 1990 academic Press, Inc.
INTRODUCTION Hemangiopericytoma was first described by Stout and Murray in 1942 [I]. It is an uncommon tumor arising
from the pericytes. This tumor may occur at any site where capillaries are found [2,3]; however, malignant hemangiopericytoma of the omentum is extremely rare. Only three well-documented cases have been previously reported in the English literature [4-71. We now report the fourth case of this tumor, the first in a woman. CASE REPORT A 62-year-old Japanese woman, gravida 4, para 3, was admitted to Shimonoseki Municipal Central Hospital with complaints of abdominal distension and pain on August 10, 1988. Her past medical history was noncontributory. Seven months prior to admission, the patient noticed increasing abdominal girth, diarrhea, and weight loss. 208 0090-8258&O$1.50 Copyright 0 1990 by Academic Press, Inc. All rights of reproduction in any form reserved.
1. 1990
Physical examination revealed a distended abdomen with a huge cystic abdominopelvic mass reaching two fingerbreadths above the navel. Pelvic examination revealed a normal external genitalia, vagina, and cervix. The uterine body was not clearly palpable due to a large abdominopelvic mass. Pelvic sonogram, CT scan, and magnetic resonance imaging showed a multilocular cyst with some solid parts and moderate ascites (Fig. 1). Laboratory tests revealed mild anemia (Hb 9.6 g/dl), a high level of LDH (738 U/liter), C-reative protein of 6.8 mg/dl, and CA-125 of 1300 U/ml. Chest X rays, intravenous pyelogram, barium enema, cystoscopy, and sigmoidoscopy were within normal limits. A malignant ovarian tumor was suspected and the patient underwent a laparotomy on August 17, 1988. About 2000 ml of yellowish ascites was present. A large cystic tumor arising from the omentum was detected (Fig. 2). Frozen-section diagnosis of this tumor was reported as leiomyosarcoma. The uterus and bilateral ovaries were grossly normal. Exploration of the abdominal cavity revealed no intraperitoneal spread. The patient underwent total omentectomy, simple hysterectomy, bilateral salpingo-oophorectomy, and biopsy of paraaortic lymph nodes. Complete resection of the tumor was performed. Cytology of ascites was negative. Final pathological diagnosis was reported as malignant hemangiopericytoma arising and localized in the omentum. Postoperatively, the patient was given ten courses of adjuvant combination chemotherapy consisting of cyclophosphamide 400 mg/m2, Adriamycin 40 mg/m2, and c&platinum 40 mg/m2 (CAP) every 4 weeks. LDH and CA-125 returned to normal and remained normal. The patient showed no
209
CASE REPORT
FIG. 1. Sagittal magnetic resonance image showing a huge multilocular cyst with some solid parts and moderate ascites. M, mass; uterus.
evidence of disease on physical examination until June 1989. However, sonogram and CT scan revealed an intraabdominal mass in July 1989 and a second laparotomy was performed on July 19, 1989. Several intraperitoneal polypoid tumors growing from the parietal peritoneum and the mesentery were recognized. PATHOLOGICAL FINDINGS Grossly, the tumor was dark and lobulated, measured 24 x 20 x 12 cm, and weighed 2400 g. It was connected to the omentum via a pedicle with some dilated vessels. The capsule had already been partly ruptured. The cut surface revealed a variegated appearance with gray-tan, gray-yellowish, and multiple hemorrhagic and/or necrotic areas. Microscopically, round or spindle-shaped tumor cells were packed around the developed vascular channels and numerous capillaries. The vessels were thin walled and lined by a single layer of flattened nonneoplastic endothelial cells (Fig. 3). Cellularity was high and nuclear atypia was moderate to severe. Many mitotic figures
U,
(12/10 HPF) were also observed (Fig. 4). The reticulin stain revealed well-developed reticular meshworks and tumor cells outside the vascular spaces (Fig. 5). The tumor cells were positive by immunocytochemical stains for vimentin, and negative for S-100 protein, myoglobin, desmin, actin, and factor VIII. Electron microscopic examination was also performed. Tumor cells showed no specific findings. The nuclei were ovoid or spindle-shaped and contained a prominent single nucleolus. The cytoplasm was scanty and mitochondria, rough endoplasmic reticulum, free ribosomes, and Golgi apparatus were present. Tumor cells were surrounded by basal lamina and separated from endothelial cells by the basement membranes; however, there were no features by which tumor cells could be differentiated from smooth muscle cells. DISCUSSION Hemangiopericytoma is a vascular tumor that arises from the pericytes surrounding the capillaries [l-3]. These tumors are uncommon, and half of them are re-
IMACHI ET AL.
FIG. 2. Large cystic tumor of the omentum and normal internal genitalia.
ported as malignant. They are most commonly found in the musculature of the lower extremities, retroperitoneum, and pelvis [2]. Malignant hemangiopericytoma arising in the omentum is extremely rare and only three well-documented cases have been reported [4-61. If we apply the criteria for uterine sarcomas [8,9], the tumor in our patient may be histologically malignant according to the findings of numerous mitoses, increased cellularity, and cytologic atypia. However, there are no definite morphological criteria on which to differentiate malignant hemangiopericytoma from benign hemangiopericytoma [3,10-121. Binder et al. [13] reported that criteria such as anaplastic nuclear changes and mitoses are not reliable for the diagnosis of malignant hemangiopericytoma. On the other hand, the number of mitotic figures, increased cellularity, presence of cellular anaplasia, and foci of hemorrhage and necrosis can help distinguish the tumors as benign or malignant [2,14]. McMaster et al. [15] classified 60 patients with he-
mangiopericytoma histologically as benign, borderline malignant, and malignant on the basis of microscopic findings such as vascular pattern, shape of pericytes, anaplasia of pericytes, number of mitotic figures, and reticulin pattern. They reported that the 16 patients with borderline malignant tumors and the 32 patients with malignant tumors had a greater degree of cellular anaplasia and a larger number of mitotic figures than the 12 patients with benign tumors. In our case, all these findings (numerous mitotic figures, cellular anaplasia, and increased cellularity) were observed. The histological features of hemangiopericytoma resemble those of hemangioendothelioma, glomus tumor, leiomyosarcoma, synovial sarcoma, chondrosarcoma, mesothelioma, liposarcoma, and malignant fibrous histiocytoma [2]. In our case, the intraoperative diagnosis by frozen section was leiomyosarcoma; however, negative immunocytochemical stains for desmin and the lack of features differentiating smooth muscle cells by elec-
CASE REPORT
211
FIG. 3. Low-power photomicrograph of the tumor showing round or spindle-shaped tumor cells around developed vascular channels and capillaries. H&E, x 40.
tron microscopic study ruled out the diagnosis of leiomyosarcoma. The incidence of recurrence and/or metastasis of malignant hemangiopericytoma is difticult to predict. Enzinger er al. [2,16] reported that the incidence of metastases varied from 12 to 56% and local recurrences preceded metastases in more than two-thirds of the patients with evidence of metastatic disease. The IO-year survival rate was 70% by Enzinger and Smith [2]. Longterm follow-up is recommended because metastases may become apparent in patients after 5 or more disease-free years [ 15,171. In particular, intraabdominal hemangiopericytomas excluding those of uterine and gastric origin are frequently malignant [13]. Metastases usually occur by the hematogenous route and lymph node metastases are rare [15]. In our patient, intraabdominal recurrence probably due to implantation was observed 11 months later; however, no distant metastasis was found. The
detailed diagnosis of the omental tumor is often made with angiography [6,18]. However, the preoperative diagnosis of malignant hemangiopericytoma of the omenturn is very difficult. In our patient, a malignant ovarian tumor was suspected preoperatively by the findings of sonogram, CT scan, magnetic resonance imaging, and a high CA-125 value. The primary therapy of this tumor should be surgical [13,15]. In our patient, total omentectomy, simple hysterectomy, bilateral salpingo-oophorectomy, and biopsy of paraaortic lymph nodes were performed. The role of chemotherapy for this tumor is not established [13]. Some have reported the efficacy of Adriamycin for malignant hemangiopericytoma [ 19-211. Our patient was treated with CAP combination chemotherapy, but the tumor recurred within 11 months. The effectiveness of radiation therapy for this tumor has not been established n31.
212
IMACHI ET AL.
FIG. 4. High-power photomicrograph of the tumor showing cytologic atypia, numerous mitoses, and increased cellularity. H&E, x 400.
REFERENCES 1. Stout, A. P., and Murray, M. P. Hemangiopericytoma: A vascular tumor featuring Zimmerman’s pericytes, Ann. Surg. 116, 26-33 (1942). 2. Enzinger, F. M., and Smith, B. H. Hemangiopericytoma: An analysis of 106 cases, Hum. Pahol. 7, 61-82 (1976). 3. Stout, A. P. Hemangiopericytoma: A study of 25 new cases, Cancer 2, 1027-1054 (1949). 4. Stout, A. P., Hendry, J., and Purdie, F. J. Primary solid tumors of the great omentum, Cancer 16, 231-243 (1963). 5. Harder, V. T., Koischwitz, D., and Engel, C. Primary tumors of the mesentery and great omentum, Forts&r. Rontgenstr. 139,274280 (1983). 6. Iijima, T., Kon, Y., Zuguchi, M., Hatakeyama, M., Takahashi, K., Heshiki, A., Ogata, N., and Harada, T. Radiological diagnosis of the omental masses, Japan. J. Clin. Radial. 28,611-614 (1983). 7. Goldberger, R. E., and Schein, C. J. Hemangiopericytoma of the omentum. Report of a case with an unique presentation and review of the literature, Amer. Surg. 34, 291-295 (1968). 8. Norris, H. J., and Taylor, H. B. Mesenchymal tumors of the uterus, Cancer 19, 755-766 (1%6).
9. Kempson, R. L., and Bari, W. Uterine sarcoma: Classification, diagnosis and prognosis, Hum. Puthol. 1, 331-349 (1970). 10. Stout, A. P. Tumors featuring pericytes, Lab. Invest. 5, 217-223 (1956). 11. Kauffman, S. L., and Stout, A. P. Hemangiopericytoma in children, Cancer 13, 695-710 (1960). 12. Kauffman, S. L., and Stout, A. P. Congenital mesenchymal tumors, Cancer 18, 460-476 (1965). 13. Binder S. C., Wolfe, H. J., and Deterling, R. A. Intra-abdominal hemangiopericytoma, Arch. Surg. 107, 536-543 (1973). 14. Hacken, J. B., and Athey, P. A. Recurrent and metastatic retroperitoneal hemangiopericytoma, J. Comput. Tomogr. 9, 257-259 (1985). 15. McMaster, M. J., Soule, E. H., and Ivins, J. C. Hemangiopericytoma: A clinicopathologic study and long-term follow-up of 60 patients, Cancer 36, 2232-2244 (1975). 16. Enzinger, F. M., and Weiss, S. W. Hemangiopericytoma, in Soft tissue tumors, Mosby, St. Louis, pp. 463-481 (1983). 17. Backwindel, K. D., and Diddams, J. A. Hemangiopericytoma. Report of a case and comprehensive review of the literature, Cancer 25, 896-901 (1970).
CASE REPORT
213
PIG. 5. Reticulin stain showing a developed reticular meshwork and tumor cells outside the vascular spaces. x 100.
18. Fataar, S., Morton, P. C. G., Schulman, A., Roman, T., and Harvey, A. Radiological diagnosis of primary greater omental mass lesions, Clin. Radiol. 32, 325-330 (1981). 19. Wong, P. P., and Yagoda, A. Chemotherapy of malignant hemangiopericytoma, Cancer 41, 1256-1260 (1978).
20. Morris, D. M., Vuthiganon, C., Chang, P., Wiemnik, P. H., and Elias, E. G. Adriamycin in management of malignant hemangiopericytoma, Amer. Surg. 47, 441-446 (1981). 21. Beadle, G. F., and Hillcoat, B. L. Treatment of advanced malignant hemangiopericytoma with combination adriamycin and DTIC: A report of four cases, .I. Surg. Oncol. 22, 167-170 (1983).