Omental-mesenteric myxoid hamartomas. Infantile lesions simulating malignant tumors.

Three infants presented with multiple nodular tumors of the omentum and mesentery characterized histologically by plump mesenchymal cells in a myxoid, well-vascularized stroma. Electron microscopy of one tumor revealed reticulated inclusions in dilated cisterna of endoplasmic reticulum. Diagnoses by the original pathologist, or by consultants from referral centers in the United States included liposarcoma, primitive sarcoma, possible leiomyosarcoma, and fibromatosis, but the subsequent evolution of the patients questions the validity of such diagnoses. Two patients received what was deemed ineffective therapy, yet survived with no evidence of disease for over a decade of close follow-up. Another patient received no therapy other than the initial surgery, and has been well for more than a year. Infantile lesions may show deceptive features of immaturity and high cellularity that are apt to be confused with a true malignancy. Omentalmesenteric "myxoid" lesions are probably hamartomatous in origin.