Basosquamous or basal cell carcinoma? The importance of the differential diagnosis

Basosquamous carcinoma (BSC) is a rare and aggressive type of basal cell carcinoma (BCC) more frequently involving head and neck region1 characterized by high tendency to recur locally or at distant sites. Metastasis have been observed with a latency period that can vary from 0 to 30 years.2 In some cases, first diagnosis of the skin lesion is consistent with BCC, and only after metastasis detection diagnosis of BSC has been done.3,4 Immunohistochemistry is useful to diagnose BSC: areas of squamous cell carcinoma are cytokeratin AE1, cytokeratin AE3, and cell adhesion molecule 52 positive and show variable staining with epithelial membrane antigen.