Malignant Melanoma of the Small Intestine Diagnosed as a Result of Bowel Intussusception and Treated by Laparoscopic Surgery

Abstract

A 36-year-old woman presented with a one-month history of watery diarrhea and periumbilical pain, and abdominal contrast-enhanced computed tomography (CT) showed wall thickening and intussusception at several sites in the small intestine. Bowel intussusception associated with multiple small bowel tumors was diagnosed, and emergency surgery was performed. Laparoscopic observation showed intussuscepted bowel with a black tumor as the presenting part, and a total of 5 tumors in the small intestine as a whole, including this one, were resected. The postoperative course was uneventful, and the patient was discharged on Day 8. Histopathological investigations led to a diagnosis of malignant melanoma, and since sacral, iliac, and multiple lung metastases were observed on PET-CT, chemotherapy with dacarbazine was started at another hospital. Primary gastrointestinal malignant melanoma is infrequent, accounting for 1.4%-1.8% of all malignant melanomas, and its primary occurrence in the small intestine is extremely rare. In the present case, systemic metastases were already present at the time of diagnosis, and the primary site was unknown, but the diagnosis of metastasis was considered appropriate. In most cases, the prognosis is hopeless, but it was considered that the laparoscopic total resection of tumors that may cause bowel intussusception, hematochezia or perforation, and the immediate postoperative start of chemotherapy were both extremely helpful.