Sclerosing angiomatoid nodular transformation of the spleen masquerading as a sarcoma metastasis

Sarcomatous malignant peritoneal mesothelioma developing in the abdominal cavity is very rare, and little is known about its behavior. A 72-year-old woman was referred to our hospital with anemia and weight loss. Tumor marker levels were within normal limits. Abdominal computed tomography showed an 11¥7 cm tumor in the pelvis, with possible invasion of the large bowel. Colonoscopy revealed a tumor protruding into the cecal lumen with an ulceration of the cecal wall. Although malignancy was suspected, the histological type was not identified in the biopsy specimens. Right hemicolectomy and ileocolic anastomosis were performed as a treatment. A postoperative histopathological examination confirmed the initial diagnosis of malignant mesothelioma. Finally, immunohistochemical examination revealed a localized sarcomatous malignant peritoneal mesothelioma with regional lymph node metastases. The patient was followed up postoperatively as an outpatient, and local recurrence was detected in the abdominal cavity 11 months after surgery. In conclusion, localized malignant peritoneal mesothelioma, especially the sarcomatous type, with large bowel involvement is very rare. We should carefully consider the diagnosis and select adequate therapy, because little is known about the behavior of this disease