basal cell carcinoma of the anal region

Basal cell carcinoma of the anal region is rare and morphologically difficult to distinguish from basaloid squamous cell carcinoma, particularly on biopsies. This distinction has therapeutic and prognostic implications.

Perianal location, retraction artifact, and lack of atypical mitoses are histological features that help distinguish basal cell carcinoma from basaloid squamous cell carcinoma.

An in situ component, when present, supports the diagnosis of basaloid squamous cell carcinoma.

Immunostains are extremely helpful as diffuse Ber-EP4 and BCL2 expression is a feature of basal cell carcinoma and basaloid squamous cell carcinoma is typified by diffuse CDKN2A and SOX2 expression.

Reference

 Clinicopathological analysis of basal cell carcinoma of the anal region and its distinction from basaloid squamous cell carcinoma. Patil DT, Goldblum JR, Billings SD. Mod Pathol. 2013 Apr 19. doi : 10.1038/modpathol.2013.75 PMID: 23599161