Bone formation in a rectal inflammatory polyp

Figure 1 Subpedunculated polyp in the lower rectum. A: Colonoscopy revealed a slightly reddish subpedunculated polyp, about 12 mm in diameter, in the lower rectum. The surface of the polyp was covered with whitish exudate, which suggested inflammatory change; B: Magnifying observation with dye-spraying using 0.4% indigo carmine revealed a type I pit pattern according to the Kudo’s classification; C: Histologically, the surface of the resected specimen was mostly covered by inflammatory exudate and partly by regenerating epithelium; D: Several foci of heterotopic bone formation were also found on histology.