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[Pancreatic Leiomyosarcoma with a Difficult Preoperative Diagnosis-A Case Report].

A 43-year-old man was referred to our hospital for examination of a pancreatic tumor. Imaging revealed a mass-like lesion with a cyst in the pancreatic tail. Histological examination by EUS-FNA showed a low grade spindle cell lesion for which laparoscopic distal pancreatectomy was performed. The neoplasm was histologically diagnosed as pancreatic leiomyosarcoma. The postoperative course was uneventful and no signs of recurrence at 8 months after the surgery. Pancreatic leiomyosarcoma is very rare. Only 7 previous cases were reported in Japan. In tumors with diameters exceeding 50 mm, bleeding and necrosis occur inside the tumor and a cyst-like form often develops, which is considered a characteristic imaging finding. Therefore, imaging is important for preoperative differential diagnosis of the disease.