1. a type of squamous cell carcinoma of the anus originating in tissues arising from, or in remnants of, the cloaca.
2. in oncology, anal cancer arising proximal to the pectinate line.
[cloaca + -genic]
Etymology: Gk, basis + eidos, form, karkinos, crab, oma, tumor
a rare transitional malignant neoplasm of the anal canal containing areas that resemble basal cell carcinoma of the skin. Basaloid carcinoma is rapidly invasive. Tumor may spread to the skin of the perineum.
A subtype of squamous cell carcinoma arising at the anorectal transition zone, which comprises 20% of all anal carcinomas. It is linked to HPV infection and more common in homosexual males, implicating anal intercourse as a vector. It has been variously reported as having either a better or worse prognosis than standard anal cancer.
A form of large cell carcinoma (non-small cell type), in which at least 50% of the cellular component is a basal cell carcinoma; it is often high-grade with 15–50 mitoses/10 HPF, and has a dismal prognosis by some authors as a type of squamous cell carcinoma.
p63, CK 5/6 +ve.
Poorly differentiated squamous cell carcinoma, small cell carcinoma, large cell neuroendocrine carcinoma.
Small cuboidal or fusiform cells; lobular or tentacular invasion, peripheral palisading.
Probably worse than stage-matched squamous cell carcinoma.
Aggressive, rapidly growing; nodes are involved in 2/3 at time of diagnosis; distant metastases frequent (37–50%); age/site/stage/treatment matched-case control studies have the same prognosis as high-grade conventional SCC.