When the whole lesion is not available formicroscopic examination and if immunohistochemistry is performed in thesecases, CK15 immunoreactivity of the cellular aggregates as well as the presenceof scattered CK20-positive cells would favour the diagnosis of trichoblastoma.In the same way, the differential expression of CD10 and Bcl2 (CD10 positive onthe stroma of trichoblastoma, but not on BCC cells; and Bcl2 immunoreactivitypositive in BCC cells, but negative in trichoblastoma cells) may be helpful inthe distinction.32,33. The gene discussed is KRT15; the disease is skin basal cell carcinoma.