An extrarenal malignant rhabdoid tumor suspected to originate from the mesentery in an adult: report of a case.

A malignant rhabdoid tumor is very rare and its prognosis is extremely poor. It was first described as a distinctive and highly malignant neoplasm of the infant kidney. Tumors with a similar appearance have been reported in various extrarenal sites. We herein report a case of a 41-year-old man who was admitted to our hospital complaining of a lower abdominal mass. After one series of examinations, the patient underwent a laparotomy. Most such tumors are situated in the mesentery and involve the small intestine, and thus we diagnosed it to originate from mesentery. This tumor could not be resected and only an excisional biopsy was done. It was histologically composed of a solid sheet arrangement with ovoid, round, and lateralized nuclei and mild acidophilic cytoplasm. Inclusion body-like structures were found in the cytoplasm. Immunohistochemically, the tumor cells were positive for cytokeratin, epithelial membrane antigen, vimentin, and CAM5.2. The patient died 2 weeks after operation due to multiple organ failure.