bcl-2 expression reliably distinguishes trichoepitheliomas from basal cell carcinomas.

Trichoepitheliomas (TE) are benign follicular neoplasms which are frequently confused with basal cell carcinomas (BCC). It is important to distinguish these entities precisely, as the treatments and prognoses are different. To this end, we stained a series of formalin-fixed, paraffin-embedded specimens of unequivocal TE and BCC with antibodies directed against bcl-2, an oncogene associated with programmed cell death, and known to be overexpressed in some malignant tumours. The TE showed staining of tumour cells limited to the outermost layer of the proliferation. The BCC tumour cells demonstrated diffuse staining throughout the tumour nodules. This difference in staining pattern was then applied to more equivocal cases, and seemed clearly to separate the entities. The observed findings may prove to be of diagnostic help in distinguishing borderline cases, and also offer some possible explanations for the biological differences between these neoplasms.