Slow-Growing Pancreatic Smooth Muscle Tumor Treated with Partial Pancreatectomy: A Case Report.

INTRODUCTION: Smooth muscle tumors, such as leiomyoma or leiomyosarcoma, are mesenchymal tumors that originate from smooth muscle cells. Smooth muscle tumors in the abdominal cavity often originate from the uterus, gastrointestinal wall, and inferior vena cava, but rarely originate from the pancreas. We present a rare case of a pancreatic leiomyoma that was successfully treated via partial pancreatectomy. CASE PRESENTATION: A 74-year-old man with a pancreatic head tumor was referred to our hospital. Imaging revealed a heterogeneous 61 × 45 mm mass with a contrast effect in the pancreatic head. Distant metastases were not detected. The tumor was diagnosed by endoscopic ultrasonography-guided fine-needle aspiration as a leiomyoma, and follow-up was planned. Five years after the initial visit, the patient developed abdominal tension, and a CT scan revealed that the tumor had grown to 80 × 60 mm. It was decided that the tumor required surgical treatment comprising pancreaticoduodenectomy. However, the intraoperative findings revealed that the tumor was able to be moved freely but was unable to be dissected from a part of the pancreatic head. Therefore, partial pancreatectomy was performed. Histopathology showed spindle-shaped tumor cells with mild atypia. Pancreatic tissue was present at the tumor margins, and the tumor was adjacent to the vasculature. Based on the clinical and pathological findings, the tumor was diagnosed as a smooth muscle tumor originating from the pancreas. The patient was discharged without complications on POD 8 and has now been doing well without recurrence for more than 6 months after surgery. CONCLUSIONS: A very rare slow-growing pancreatic smooth muscle tumor was removed via partial pancreatectomy after the patient developed abdominal symptoms after a 5-year observation period.