Retroperitoneal Fibromatosis in a Cynomolgus Monkey (Macaca fascicularis)

Abstract

A palpable abdominal mass was found in a 4-year-old female cynomolgus monkey (Macaca fascicularis) with chronic anorexia. Grossly, there were numerous coalescing firm nodular lesions, 1 to 5 cm, scattered in the omentum and mesentery. Histologically, there was prominent infiltrative growth of fibroblastic cells with a large amount of collagen fibers in the nodular lesions involving the intestinal tract. The morphological features of the lesion were similar to those of retroperitoneal fibromatosis (RF) in SRV-2-infected macaques, and also closely resembled those of peritoneal desmoid tumor in human. This macaque case is possibly the first reported case of RF in Japan.