Basaloid-squamous cell carcinoma of the bronchus. Report of a case with review of the literature.

Basaloid-squamous cell carcinoma (BSCC) is a variant of squamous cell carcinoma with biphasic basaloid and squamous features. Recognition of BSCC is important because this lesion can be confused with less aggressive lesions, such as adenoid cystic carcinoma. BSCC is typically detected at an advanced stage in smokers, alcoholics, and older individuals; adenoid cystic carcinoma is not associated with smoking or alcohol, and it typically occurs in younger individuals. Approximately 88 cases of BSCC in the upper aerodigestive tract have been recorded since its first description in 1986. We report one case of endobronchial BSCC. Cytologically, both squamous and basaloid features were identified, including elongated, irregular, globular, extracellular, hyaline material. Immunohistochemical studies showed two distinct populations of cells: the squamous component, positive for cytokeratin (AE1 + AE3) and negative for smooth-muscle actin, epithelial membrane antigen, S100 protein, and type IV collagen; and the basaloid component, positive for all of the above markers, with minimal staining for cytokeratin (AE1 + AE3). The electron microscopy demonstrated desmosomes in the squamous component and replication of the basal lamina in the basaloid component. We conclude that BSCC of the bronchus is similar to BSCC in the upper aerodigestive tract and should be regarded as a distinct entity.