Genetic Analysis of a Trichoepithelioma and Associated Basal Cell Carcinoma

Trichoepithelioma (TE) is a benign skin tumor originating from hair follicles and is most commonly found on the face. It may occur as a solitary nonfamilial or a multiple-familial type.¹ The histological features of TE are dermal aggregates of basaloid cells with connection to or differentiation toward hair follicles. Differentiation between TE and basal cell carcinoma (BCC) may be difficult or even impossible.² The genes for both hereditary BCC and hereditary TE have been recently identified.^1,3 In hereditary BCC, patients carry BCC gene mutations at 9q22.3, and genetic alterations of the other BCC allele are believed to initiate tumorigenesis.³ In multiple-familial TE, the causative gene has been mapped to 9p21.¹ In sporadic BCC, gene alterations also appear to play a role in the tumorigenesis. In 50% of sporadic BCCs, deletions at the BCC locus have been demonstrated.⁴ Only 1 case of a solitary TE showing a deletion at the BCC locus⁵ has been reported in the literature.³