Background A recent small series demonstrated perfect sensitivity and specificity utilizing immunostaining for PHLDA1, a marker of follicular stem cells, in the distinction of desmoplastic trichoepithelioma and morphoeiform basal cell carcinoma (BCC) in small biopsy specimens.
Objectives To assess this result more broadly.
Methods We performed immunoperoxidase staining of BCCs (superficial n = 16, nodular n = 15, micronodular n = 15, infiltrative n = 17, morphoeiform n = 16, infundibulocystic n = 14) and trichoepitheliomas (conventional n = 19, desmoplastic n = 16) with PHLDA1.
Results Morphoeiform BCCs typically lacked PHLDA1 staining (88% demonstrated no staining and 12% of cases had staining in < 25% of the tumour), while in contrast 74% of classical and 88% of desmoplastic trichoepitheliomas demonstrated strong PHLDA1 staining in over half of the tumour. However, micronodular BCCs demonstrated focal to diffuse positive staining in a third of the cases.
Conclusions Based upon our staining results, we discuss the biological significance of PHLDA1 expression and the limits in its diagnostic utility.