Difference between revisions of "Squamous metaplasia of the rectum/anus"
Jump to navigation
Jump to search
| Line 5: | Line 5: | ||
==General== | ==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> | *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> | ||
Anatomy & histology: | |||
*Typically, the squamocolumnar junction is just above the dentate line (also ''pectinate line''). | |||
*Squamous epithelium 1 cm proximal to the dentate line is considered abnormal.<ref name=pmid11174313>{{Cite journal | last1 = Bujanda | first1 = L. | last2 = Iriondo | first2 = C. | last3 = Muñoz | first3 = C. | last4 = Etxezarraga | first4 = C. | last5 = Ramírez | first5 = MM. | last6 = Ramos | first6 = F. | last7 = Sánchez | first7 = A. | title = Squamous metaplasia of the rectum and sigmoid colon. | journal = Gastrointest Endosc | volume = 53 | issue = 2 | pages = 255-6 | month = Feb | year = 2001 | doi = | PMID = 11174313 }}</ref> | |||
*The dentate line divides the anal canal into upper two thirds and lower third. | |||
==Microscopic== | ==Microscopic== | ||
Revision as of 02:41, 16 June 2016
Squamous metaplasia of the rectum/anus is a metaplastic change of the columnar epithelium of the rectum.
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]
Anatomy & histology:
- Typically, the squamocolumnar junction is just above the dentate line (also pectinate line).
- Squamous epithelium 1 cm proximal to the dentate line is considered abnormal.[2]
- The dentate line divides the anal canal into upper two thirds and lower third.
Microscopic
Features:
- Uniform cell spacing - no crowding - key feature.
- Nuclei are uniform size and round.
- +/-Nucleoli present.
- 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
ISM - very low mag.
ISM - low mag.
ISM - intermed. mag.
ISM - high mag.
IHC
- p16 -ve
- Usually weak-to-moderate patchy, not full thickness.
- Ki-67 - scattered cells positive.
See also
References
- ↑ 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.
- ↑ Bujanda, L.; Iriondo, C.; Muñoz, C.; Etxezarraga, C.; Ramírez, MM.; Ramos, F.; Sánchez, A. (Feb 2001). "Squamous metaplasia of the rectum and sigmoid colon.". Gastrointest Endosc 53 (2): 255-6. PMID 11174313.