Case Number : Case 3022 - 4 February 2022 Posted By: Dr. Richard Carr

infiltrative basosquamous cell carcinoma

BCC. First pic shows epithelial-stromal retraction, and more basaloid features. Furthermore, too much mucin

BerEP4 is negative, EMA is positive, p53 is diffuse positive in the tumor

is it Basaloid squamous cell carcinoma

Ok. But I’m waiting for Richard’s comment. It could be a follicular scc, with this stromal mucin.  

This is a basaloid SCC (rather BCC-like) and in my experience it is very unusual to see stromal mucin like this in SCC. BerEP4 is negative and EMA is widely positive. Interestingly the p16 is aberrant null in the tumour and also has highly aberrant diffuse staining for p53 so possibly has a mutation that has caused the protein to be sequestered. Not sure if this a follicular SCC or NOS. It does have a raining down pattern from the epidermis (seen in the p16) which I did not photograph for H&E in order to confuse you in to calling it a BCC. Even if this was a BCC (by IHC) I think you should consider calling it the basosquamous / metatypical variant - especially as we have dual highly aberrant p16 & p53 which is unusual in BCC (often show patchy mosaic for p16). It would be interesting to study basosquamous variants of BCC to see if they have a greater rate of highly aberrant p16/p53 (which I suspect they do, similar to SCC on severely sun-damaged skin). 

Thanks a lot sir, for learning points, morphology has limitations