Sporadic trichoepithelioma demonstrates deletions at 9q22.3

Background: Trichoepithelioma (TE) is a benign cutaneous tumor that origina tes from hair follicles and occurs either in multiple or solitary lesions. Multiple TE is transmitted as an autosomal dominant trait, and a region at 9p21 is thought to be involved in the tumorigenesis. Solitary TE occurs mor e commonly than multiple TE and is not inherited. Histologically, TE tumors contain horn cysts and abortive hair papillae. A basal cell carcinoma appe arance in some or all regions of a TE tumor can happen. In sporadic basal c ell carcinoma, frequent deletions at 9q22.3 (Drosophila patched gene) have occurred. The objective of this study is to test whether loss of heterozygo sity (LOH) on either 9p21 or on chromosome 9q22.3 could be detected in arch ival sporadic TE. Observations: We studied 29 randomly selected cases of sporadic TE by micro dissection and polymerase chain reaction using paraffin-embedded, formalin- fixed tissue specimens on glass slides. Analysis was performed with the pol ymorphic markers IFNA and D9S171 (9p21) as well as D9S15, D9S303, D9S287, a nd D9S252 (9q22.3). Results: The LOH at 9q22.3 was identified in 14 (48%) of 29 cases with at l east 1 marker, while LOH could not be demonstrated using the markers IFNA a nd D9S171 (9p21). Conclusions: The results show that the Drosophila patched gene LOH can be f requently identified in paraffin-embedded sporadic TE after routine process ing and indicates a common gatekeeper mechanism for both TE and basal cell carcinoma.