Juvenile polyps with osseous metaplasia treated by endoscopic mucosal resection

A 17-year-old male with no previous medical history presented with a 1-year history of rectal bleeding, mucus discharge and occasional rectal prolapse. Colonoscopy revealed several polypoidal growth masses in the distal rectum, formed by multiple sessile polyps with a glistening mucus-covered surface and fleshy, friable appearance, that coalesced forming large conglomerates. Given their complexity and large size, piecemeal endoscopic mucosal resection of the rectal lesions was performed and histopathological examination revealed ulcerated polypoid mucosa with mixed inflammatory cell infiltrate in the lamina propria and dilated cystic mucus-filled glands. Remarkably, bony trabeculae surrounded by osteoblastic cells were also seen. These findings were consistent with juvenile polyps with foci of osseous metaplasia. Osseous metaplasia has been described in a wide variety of tissue types, such as prostate, uterus, breasts, lungs and urinary tract, with respect to both neoplastic and non-neoplastic conditions. However, it is exceedingly rare in colonic polyps and, to the best of our knowledge, only 9 cases have been described in juvenile polyps.