ELECTRONIC CLINICAL CHALLENGES AND IMAGES IN GI Grace Elta and Robert J. Fontana, Section Editors

Peculiar Pigmented Polyp Seth Sweetser,1 John T. Woosley,2 and Todd H. Baron3 1 Division of Gastroenterology and Hepatology, Mayo Clinic College of Medicine, Rochester, Minnesota; 2Department of Pathology and Laboratory Medicine and 3Division of Gastroenterology and Hepatology, University of North Carolina School of Medicine, Chapel Hill, North Carolina

Question: A 55-year-old woman with chronic constipation underwent screening colonoscopy. The colonic mucosa had a diffuse brown pigmentation consistent with melanosis coli. In the cecum a 1-cm, Paris class IIa lesion with a yellowish hue and concomitant brown discoloration was found (Figure A). The superficial lesion was completely resected using standard hot-snare polypectomy technique. Histopathology is shown (Figure B). What is the lesion and cause of the pigmentary changes in the polyp? See the Gastroenterology web site (www.gastrojournal.org) for more information on submitting your favorite image to Clinical Challenges and Images in GI.

Conflicts of interest The authors disclose no conflicts. © 2015 by the AGA Institute 0016-5085/$36.00 http://dx.doi.org/10.1053/j.gastro.2014.11.035

Gastroenterology 2015;149:e1–e2

ELECTRONIC CLINICAL CHALLENGES AND IMAGES IN GI Answer to: Image 1: Melanosis of Sessile Serrated Polyp Figure A shows a pigmented sessile serrated polyp (SSP). Figure B demonstrates a serrated colonic crypt (arrowhead) with the brown pigmentation of melanosis coli (arrows) in the SSP. Melanosis coli is the characteristic brownish pigmentation of the colonic mucosa that is frequently found in patients who chronically use anthraquinone laxatives. Anthraquinone can induce apoptosis of colonic epithelial cells which are subsequently phagocytosed by macrophages.1 The term melanosis coli was coined by Virchow in 1857 because the pigment was thought to be melanin. The pigmentation is actually caused by the accumulation of the degradation substance lipofuscin in macrophages of the lamina propria.2 Colonic neoplasms typically lack pigment-containing macrophages and therefore are more easily visualized in patients with melanosis coli.3 SSPs can have a subtle endoscopic appearance and require careful inspection for detection and it may be assumed that colonoscopic detection of SSPs in patients with melanosis coli can be facilitated by the absence of pigmentation in these polyps. However, this case highlights that SSPs can have melanosis and, therefore, the lack of pigmentary mucosal changes cannot be relied upon as factor to distinguish an SSP from non-neoplastic pigmented mucosa.

References 1. 2. 3.


Walker NI, Bennett RE, Axelsen RA. Melanosis coli. A consequence of anthraquinone-induced apoptosis of colonic epithelial cells. Am J Pathol 1988;131:466–476. Benavides SR, Morgante PE, Monserrat AJ, et al. The pigment of melanosis coli: a lectin histochemical study. Gastrointest Endosc 1997;46:131–138. Morganstern L, Shemen L, Allen W, et al. Melanosis coli: changes in appearance when associated with colonic neoplasia. Arch Surg 1983;118:62–64.

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