Solitary fibrous tumor of the pancreas: case report with cytologic and surgical pathology correlation and review of the literature.

CONTEXT Solitary fibrous tumor is an uncommon spindle cell tumor which can occur in a variety of locations. Four cases of pancreatic solitary fibrous tumor have been reported in the literature. CASE REPORT We report the fifth case of pancreatic solitary fibrous tumor in a 78-year-old woman who presented with back pain and weight loss. Imaging studies were suggestive of an endocrine tumor. Endoscopic ultrasound with fine needle aspiration was performed and revealed a benign mesenchymal tumor, which is the first successful report of cytology on a pancreatic solitary fibrous tumor. The patient underwent a distal pancreatectomy with resection of the mass which was diagnosed as solitary fibrous tumor, supported by immunohistochemical studies showing positivity for CD99, vimentin, bcl-2, and CD34. CONCLUSION Diagnosing pancreatic solitary fibrous tumor is challenging due to its rarity, nonspecific clinical presentation, and difficulty to be radiologically distinguished from other pancreatic lesions. These issues as well as the prior four cases are discussed.