Primary leiomyosarcoma of the pancreas: study of 9 cases and review of literature.

Primary pancreatic leiomyosarcomas are rare lesions and not well described, yet they are the most common primary pancreatic sarcoma. English-language medical literature reports 29 cases as single cases or small series. A systematized nomenclature of medicine (SNOMED) search of Mayo Clinic surgical pathology files from 1994 to 2006 identified 22 primary pancreatic leiomyosarcomas. Nine patients with pancreatic leiomyosarcoma were diagnosed and treated at our institution (5 males and 4 females; mean age at diagnosis, 63 y; range, 39 to 87 y) are described, with a literature review. In situ hybridization for Epstein-Barr virus (EBV)-encoded RNA (EBER) was conducted in all cases to exclude EBV-associated smooth muscle tumor (EBV-SMT). Seven of the 9 patients presented with abdominal pain, weight loss, and jaundice. Seven tumors (mean, 10.7 cm; range, 1.0 to 30 cm) were located in the pancreatic head and 2 in the tail. Histologic findings of primary pancreatic leiomyosarcomas (7 spindle and 2 epithelioid) were similar to leiomyosarcomas of other sites. All tumors stained positive for smooth muscle actin and desmin and negative for KIT. No case showed EBER positivity. Pancreaticoduodenectomy was done in 4 patients; 3 patients had palliative procedures, and 2 had biopsy only. No lymph node metastasis was identified in 4 resected tumors, but liver metastases were present in 4 patients. All patients died; 5 deaths were known to be disease related (overall mean survival, 31 months; range, 5 to 98 mo). Historical cases showed similar clinicopathologic findings. These pancreatic leiomyosarcoma lesions have the same morphologic features as their counterparts of other sites. EBER testing should be conducted--especially for pediatric patients--to rule out EBV-SMT. The tumor is likely to metastasize to liver but not regional lymph nodes. Extensive surgical resection should be advocated, even when morphologic results show a low-grade lesion.