Difference between revisions of "Squamous metaplasia of the rectum/anus"

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'''Squamous metaplasia of the anus''' is a metaplastic change of the columnar epithelium. It can histologically mimic [[anal intraepithelial neoplasia]] (AIN), especially. [[high-grade squamous intraepithelial lesion]] (HSIL).
'''Squamous metaplasia of the anus''' is a metaplastic change of the columnar epithelium. It can histologically mimic [[anal intraepithelial neoplasia]] (AIN), especially. [[high-grade squamous intraepithelial lesion]] (HSIL).
==General==
*Present in the transformation zone between the columnar epithelium of the [[rectum]] and squamous epithelium of the [[anus]] - similar to the transformation zone of the [[uterine cervix]].<ref name=pmid20436833>{{Cite journal  | last1 = Pineda | first1 = CE. | last2 = Welton | first2 = ML. | title = Management of anal squamous intraepithelial lesions. | journal = Clin Colon Rectal Surg | volume = 22 | issue = 2 | pages = 94-101 | month = May | year = 2009 | doi = 10.1055/s-0029-1223840 | PMID = 20436833 }}</ref>


==Microscopic==
==Microscopic==

Revision as of 02:18, 16 June 2016

Squamous metaplasia of the anus is a metaplastic change of the columnar epithelium. It can histologically mimic anal intraepithelial neoplasia (AIN), especially. high-grade squamous intraepithelial lesion (HSIL).

General

  • Present in the transformation zone between the columnar epithelium of the rectum and squamous epithelium of the anus - similar to the transformation zone of the uterine cervix.[1]

Microscopic

Features:

  • Uniform cell spacing - no crowding - key feature.
  • Nuclei are uniform size and round.
  • Distinct cell borders
  • +/-Intercellular bridges (due to edema) - common.

Negatives:

  • No mitoses/rare basal mitoses - think cancer/AIN if you see 'em.
  • Usually no hyperchromatism (think cancer/CIN if you see it).

DDx:

Images

IHC

  • p16 -ve
    • Usually weak-to-moderate patchy, not full thickness.
  • Ki-67 - scattered cells positive.

See also

  1. Pineda, CE.; Welton, ML. (May 2009). "Management of anal squamous intraepithelial lesions.". Clin Colon Rectal Surg 22 (2): 94-101. doi:10.1055/s-0029-1223840. PMID 20436833.