A case of huge cystic gastrointestinal stromal tumor of the small intestine with CA125 elevation and pseudo-meigs syndrome which was difficult to differentially diagnose with an ovarian tumor

A 60-year-old woman complained of abdominal distension. Ultrasonography, computed tomography and magnetic resonance imaging revealed a huge tumor with solid and cystic regions, accompanied with pleural effusion and ascites. The serum level of CA125 was elevated. These findings suggested a primary ovarian cancer. At laparotomy, ovary and uterus were intact, and a tumor 20 cm in size was found to originate from the jejunum and invade the urinary bladder. The extramural tumor of the jejunum was resected, and pleural effusion and ascites disappeared after the operation. The fascicular spindle-shaped tumor cells were found to be histopathologically positive for c-kit immunohistochemical staining, yielding a diagnosis of a cystic gastrointestinal stromal tumor of the small intestine. Preoperative differential diagnosis from ovarian tumor was difficult in this case. This is considered to be the first case of pseudo-Meigs syndrome caused by a small intestinal GIST in Japan.