Unusual course of colonic tattooing with India ink.

We here report the successful but unusual course of colonic tattooing in a patient with a carcinoma in situ in a polyp. A 70-year-old woman was admitted for persistent diarrhea, occult fecal blood, and anemia. During colonoscopy, a pedunculated large polyp in the sigmoid colon occluding the lumen was removed successfully. Histopathological examination revealed a carcinoma in situ with a resection of the peduncle in sano. At the second sigmoidoscopy, the polypectomy site was marked with India ink to facilitate the recovery of the polypectomy site in follow-up endoscopies. Three months later, the India ink had spread in the submucosal layer and a segment measuring 15 cm was colored dark blue. At the original polypectomy site, an uncolored flat mucosal proliferation was found above the dark colonic wall. After mucosectomy, the tissue was classified as hyperplastic. Six weeks later, a second control sigmoidoscopy did not show any suspicious mucosal alterations.