A primary extraskeletal osteosarcoma of the mesentery: a case report

Extraskeletal osteosarcoma is a rare and invasive malignancy, typically located in the soft tissue without attachment to the skeleton. The present study reports a case of a primary mesenteric extraskeletal osteosarcoma of a 71-year-old woman. The patient complained of an incomplete defecation. Colonoscopy showed an ulcer with impression of external compression of the sigmoid. An additional abdominal computed tomography (CT) scan revealed a large, almost completely calcified, mass in the left lower abdomen causing hydronephrosis of the left kidney. The patient underwent surgery and the mass was resected completely. The histopathological diagnosis was a primary abdominal extraskeletal osteosarcoma arising from the mesocolon with local invasion of the sigmoid. She was in follow-up without adjuvant chemo- or radiotherapy. Five months after initial surgery the tumor recurred with widespread peritoneal metastasis.