A case of gastrointestinal stromal tumor of the stomach mimicking cystadenocarcinoma of the pancreas

Abstract

We report a case of gastrointestinal tumor (GIST) of the stomach, which was difficult to differentiate from cystadenocarcinoma of the pancreas, in an 82-year-old woman. She was admitted to our hospital complaining of epigastralgia and vomiting. Abdominal contrast-enhanced CT scan showed a heterogeneously enhanced tumor and cyst, located between the posterior gastric wall and pancreatic body. MRCP revealed complete pancreatic duct obstruction. FDG-PET showed abnormal accumulation only in the left upper quadrant mass. These findings suggested cystadenocarcinoma of the pancreas rather than GIST of the stomach. At laparotomy, we diagnosed an extragastric growing type GIST with invasion to the pancreatic body by frozen section, then performed a partial resection of the stomach and distal pancreatectomy. Histological findings included spindle cells with a storiform pattern and numerous mitoses (more than 10/50HPF). Immunohistochemically, the tumor was positive for c-kit and CD34, but negative for SMA, S-100 protein and desmin. In addition, she was diagnosed as having GIST of the stomach with high malignant potential, but no signs of recurrence have been observed to date, 14 months after the operation.