Differentiation between basal cell carcinoma and trichoepithelioma by immunohistochemical staining of the androgen receptor: an overview

Clinical and histopathological differentiation between basal cell carcinoma (BCC) and trichoepithelioma (TE) is a frequent problem. Attempts have been made to identify immunohistochemical markers helpful in differentiating them. A correct diagnosis is important because the tumours are treated differently. Recent studies showed the absence of androgen receptor (AR) expression in benign hair follicle tumours like TE. This study examines whether AR immunostaining is a useful diagnostic test to differentiate between BCC and TE. We randomly selected 75 cases with histological diagnoses of either BCC (subtypes: superficial, nodular or infiltrative) or TE (subtypes: classic or desmoplastic) from the database of the pathology department of Maastricht University Medical Centre. The available haematoxylin & eosin (H&E) slides were reviewed by three independent investigators using predetermined characteristics. Fifty-six slides (38 BCC and 18 TE) with unequivocal histological characteristics of either tumour were used for immunohistochemistry with AR antibodies. Any nuclear expression within the tumour was considered positive. AR expression was present in 5/8 classic TE, 0/10 desmoplastic TE, 22/23 superficial or nodular BCC and in 10/15 infiltrative BCC. Immunohistochemical stain for AR is useful to differentiate between TE and BCC; particularly in desmoplastic TE versus infiltrative BCC (specificity and positive predictive value of 100%).