Pseudomelanosis coli

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Pseudomelanosis coli
Diagnosis in short

Pseudomelanosis coli. H&E stain.

Synonyms melanosis coli

LM brown granular pigment in the lamina propria, abundant
LM DDx hemorrhage, melanocytic lesion (rarely)
Stains PAS +ve, Prussian blue -ve, Fontana-Masson +ve
Site colon, cecum, occasionally small intestine

Clinical history use of laxatives and herbals
Endoscopy brown discolouration of the mucosa, esp. proximal colon and cecum
Prognosis benign
Clin. DDx colitis
Pseudomelanosis coli
External resources
Wikipedia melanosis coli

Pseudomelanosis coli, also known as melanosis coli,[1] is a relatively common benign change seen in the colon.

General

  • Not melanin as the name melanosis coli suggests; it is actually lipofuscin (in macrophages).[2]
  • Endoscopist may see brown pigmentation of mucosa and suspect the diagnosis.
  • Presence may lead to endoscopic misinterpretation of colitis severity.[3]

Epidemiology

Gross

  • Brown pigmentation of the mucosa, especially cecum and proximal colon.[2]
    • Less pigmentation distal.

Note:

Endoscopic image

Microscopic

Features:

  • Brown granular pigment - in the lamina propria.
    • Typically more prominent in the cecum and proximal colon.[2]

Notes:

  • DDx of brown pigment:
    • Lipofuscin - comes with age (can be demonstrated with a PAS stain[5] or Kluver-Barrera stain[6]).
      • Melanosis coli.
    • Old haemorrhage, i.e. hemosiderin-laden macrophages (may be demonstrated with Prussian blue stain[7]).
    • Melanin (from melanocytes) - rare in colon (may be demonstrated with a Fontana-Masson stain[8]).
      • Fontana-Masson not useful for differentiating from pseudomelanosis, as pseudomelanosis is Fontana-Masson positive.[9]
    • Foreign material (e.g. tattoo pigment) - not seen in GI tract.

Images

Another case:

Stains

Note:

  • Fontana-Masson stain is not useful for differentiating pseudomelanosis from true melanin pigment, as pseudomelanosis is Fontana-Masson positive.[9]

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ASCENDING COLON, BIOPSY:
- PSEUDOMELANOSIS COLI.
- NEGATIVE FOR ACTIVE COLITIS.
- NEGATIVE FOR DYSPLASIA.

See also

References

  1. URL: http://www.medicinenet.com/melanosis_coli/article.htm. Accessed on: 4 March 2011.
  2. 2.0 2.1 2.2 2.3 2.4 Freeman HJ (July 2008). ""Melanosis" in the small and large intestine". World J. Gastroenterol. 14 (27): 4296-9. PMID 18666316. http://www.wjgnet.com/1007-9327/14/4296.asp.
  3. Zapatier, JA.; Schneider, A.; Parra, JL. (Dec 2010). "Overestimation of ulcerative colitis due to melanosis coli.". Acta Gastroenterol Latinoam 40 (4): 351-3. PMID 21375218.
  4. 4.0 4.1 Pardi, DS.; Tremaine, WJ.; Rothenberg, HJ.; Batts, KP. (Apr 1998). "Melanosis coli in inflammatory bowel disease.". J Clin Gastroenterol 26 (3): 167-70. PMID 9600362.
  5. Kovi J, Leifer C (July 1970). "Lipofuscin pigment accumulation in spontaneous mammary carcinoma of A/Jax mouse". J Natl Med Assoc 62 (4): 287–90. PMC 2611776. PMID 5463681. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2611776/pdf/jnma00512-0077.pdf.
  6. URL: http://education.vetmed.vt.edu/curriculum/VM8054/labs/Lab2/Examples/exkluvbarr.htm. Accessed on: 5 May 2010.
  7. URL: http://education.vetmed.vt.edu/curriculum/VM8054/labs/Lab2/Examples/exprussb.htm. Accessed on: 5 May 2010.
  8. URL: http://education.vetmed.vt.edu/curriculum/VM8054/labs/Lab2/Examples/exfontana.htm. Accessed on: 5 May 2010.
  9. 9.0 9.1 Park, C.; Cho, NH.; Jeong, HJ. (Mar 1990). "Melanosis coli--histochemical and immunohistochemical comparison of the pigments of melanosis coli and Dubin-Johnson syndrome.". Yonsei Med J 31 (1): 27-32. PMID 2346038.
  10. Benavides SH, Morgante PE, Monserrat AJ, Zárate J, Porta EA (August 1997). "The pigment of melanosis coli: a lectin histochemical study". Gastrointest. Endosc. 46 (2): 131–8. PMID 9283862.