A case of metastatic hemangiopericytoma occurring 16 years after initial presentation: with special reference to the clinical behavior and treatment of metastatic hemangiopericytoma.

A 40-year-old woman was referred to our Department of Surgery because of an abdominal wall mass. Sixteen years earlier, she had undergone surgical resection of an inguinal tumor that had been diagnosed as a hemangiosarcoma. Fourteen months after the initial resection, the tumor recurred locally, and complete resection was performed. Twenty-nine months later, computed tomography showed multiple metastatic tumors in the lung. All these tumors were resected during thoracoscopic surgery. Thirteen years after the patient's 3rd operation, a firm mass was detected in the left lower quadrant of the abdominal wall. Magnetic resonance image showed a well-defined mass with heterogeneous contrast enhancement within the rectus abdominis muscle. Positron emission tomography-computed tomography demonstrated no recurrent tumors other than this mass. Complete resection was performed. Microscopic examination showed that this tumor was composed of hypercellular spindle cells and staghorn-shaped blood vessels. The average number of mitotic figures was 28 per 10 high-power fields. Immunohistochemical examination of the tumor showed focal positivity for CD34. Therefore, the tumor was diagnosed as a metastatic hemangiopericytoma with malignant potential. Careful long-term follow-up is required because metastases can develop after an extended disease-free interval. Aggressive surgical treatment is recommended for distant metastases.