Heterotopic ossification of the intestinal mesentery. Report of a case following intraabdominal surgery.

In a 55-year-old male a nodular mass of heterotopic ossification developed in the intestinal mesentery two weeks after coloproctectomy for severe ulcerative colitis. The lesion was located close to the ileostoma where it encroached upon the intestinal wall and led to luminal obstruction. Histological examination of the tumour mass showed actively proliferating mesenchymal cells forming irregular areas of primitive osteoid and bone. The process appeared consistent with an early stage of heterotopic ossification where the short history explains the absence of the "zone phenomenon" usually characterizing such lesions. By reviewing the literature the reported case appears unique as other cases of intraabdominal heterotopic ossification have not been encountered.