Osseous metaplasia in a tubular adenoma of the colon

An 85 year old woman presented with a one month history of change in her bowel habits in the form of alternating diarrhoea and constipation. She also noted some rectal bleeding. Flexible sigmoidoscopy revealed a 1.5 cm polyp 30 cm from the anus. The polyp was removed during the sigmoidoscopy by electrocautery and sent for histological examination. The polyp was a tubular adenoma with mild dysplasia. The adenoma contained numerous foci of metaplastic bone. These consisted of irregular islands of mineralised osteoid bone rimmed by a layer of scattered osteoblasts. This is the first case of osseous metaplasia in a tubular adenoma of the colon to be reported.