basosquamous carcinoma

Basosquamous carcinoma is a controversial entity which can be defined as a basal cell carcinoma differentiating into a squamous cell carcinoma.

It is composed of three types of cell:
 basaloid cells, which are slightly larger, paler and more rounded than the cells of a solid basal cell carcinoma;
 squamoid cells with copious eosinophilic cytoplasm;
 an intermediate cell which resembles that seen in metatypical tumors.

Accordingly, the basosquamous carcinoma is sometimes confused with metatypical and keratotic basal cell carcinomas.

It is an aggressive lesion with metastatic potential.

This tumor shows some areas of Ber EP4 positivity, in contrast to squamous cell carcinoma which is always negative.