SOX9 expression is a general marker of basal cell carcinoma and adnexal-related neoplasms.

Background: SOX9 is a transcription factor that fulfills multiple functions during development. In the hair follicle SOX9 is expressed in the outer layer of the epithelial sheath, and the hair stem cell compartment. Recent data suggest that Sox9 acts as a downstream target of the Sonic hedgehog (Shh) pathway. Activation of the Shh pathway is a major cause of cutaneous basal cell carcinoma (BCC). Here we test whether activation of SOX9 is a general feature of BCC, or whether it could be used as a biomarker to better define subtypes of these skin tumors. In addition we investigated SOX9 expression in other skin epidermal tumors.

Methods: Tumors sections were stained with hematoxylin & eosin (H&E). SOX9 activation was determined by immunofluorescence.

Results: SOX9 activation was observed in all subtypes of BCC tested. Staining was heterogeneous and could be detected among the basaloid cells of the palisading cell layer as well as in the tumour nest. SOX9 expression was detected in all adnexal tumors analyzed and absent in Bowen's disease and Merkel tumor.

Conclusions: SOX9 expression is a general feature of BCC and adnexal skin neoplasms, suggesting a contribution of SOX9 to the pathogenesis of these tumors.