Colon (tumor & nontumor)
Other nonneoplastic
Melanosis coli

Topic Completed: 1 October 2013

Revised: 9 January 2019, last major update October 2013

Copyright: (c) 2003-2018,, Inc.

PubMed Search: melanosis coli

Raul S. Gonzalez, M.D.
Page views in 2019: 8,918
Page views in 2020 to date: 3,978
Cite this page: Gonzalez R. Melanosis coli. website. Accessed August 6th, 2020.
Definition / general
  • Deposition of dark melanin-like pigment in colonic macrophages after ingestion of laxatives
  • Common endoscopic finding
  • Can involve all parts of colon and rectum, but typically spares mucosal regions with lymphoid nodules, polyps or carcinomas
  • Should biopsy nonpigmented regions in these patients
  • Linked to use of anthraquinone laxatives, but may be secondary to any increase in colonic epithelium apoptosis (Histopathology 1997;30:160)
Clinical features
  • Colonoscopy
Case reports
Clinical images

Images hosted on other servers:

Darkly pigmented colonic mucosa

Colonoscopic appearance

Colon appeared dark brown and black

Gross description
  • Diffuse brown-black discoloration of colonic mucosa
Microscopic (histologic) description
  • Diffuse deposition of "melanized ceroid" in macrophages of lamina propria (Gastrointest Endosc 1997;46:131)
  • Silver stains may show abnormalities of myenteric plexus
Microscopic (histologic) images

Images hosted on PathOut server:

Contributed by Yuri Tachibana, M.D., Nagasaki University

Pigment in lamina propria

Images hosted on other servers:

Accumulation of brown melanosis pigment

Pigment laden macrophages in colonic mucosa

Macrophages engorged with brown pigment

Colonic mucosa

Positive stains
Negative stains

Melanosis coli

Differential diagnosis
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