Colon
Other nonneoplastic
Melanosis coli


Topic Completed: 1 February 2021

Minor changes: 1 February 2021

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PubMed Search: melanosis coli

Raul S. Gonzalez, M.D.
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Cite this page: Gonzalez RS. Melanosis coli. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colonmelanosis.html. Accessed April 15th, 2021.
Definition / general
  • Deposition of dark melanin-like pigment in colonic macrophages
Essential features
  • Pigment deposition in colon with striking gross and macroscopic features but minimal direct clinical consequences
  • Linked to use of anthraquinone laxatives
  • Common endoscopic finding
Sites
  • 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
Etiology
  • Linked to use of anthraquinone laxatives but may be secondary to any increase in colonic epithelium apoptosis (Histopathology 1997;30:160)
Clinical features
Diagnosis
  • Colonoscopy
Case reports
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

Contributed by Raul S. Gonzalez, M.D. and Yuri Tachibana, M.D.

Melanosis coli

Pigment in lamina propria

Positive stains
Negative stains
Videos

Melanosis coli

Sample pathology report
  • Random colon, biopsy:
    • Colonic mucosa with melanosis coli, otherwise within normal limits
Differential diagnosis
  • Blue / green / red bowel:
    • Coloration different
    • No histologic changes
  • Brown bowel / ceroidosis:
    • Pigment in smooth muscle cells
  • Hemochromatosis:
    • Pigment in epithelial cells
  • Pseudomelanosis:
    • Black pigment in macrophages of duodenum
Board review style question #1

This finding in the colon is typically secondary to

  1. Chronic granulomatous disease
  2. Laxative use
  3. Metastatic melanoma
  4. Pica
Board review style answer #1
B. Laxative use

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