Basaloid Squamous Cell Carcinoma of the Upper Aerodigestive Tract

Basaloid squamous cell carcinoma (BSCC) is an uncommon variant of squamous cell carcinoma (SCC), usually occurring in the larynx, hypopharynx, oropharynx and esophagus. BSCCs have been reported from various geographic areas, but esophageal BSCCs are more prevalent in Asia. The morphology of BSCC is quite characteristic, but BSCC occasionally needs to be differentiated from neuroendocrine carcinoma or adenoid cystic carcinoma. Human papillomavirus16-associated oropharyngeal SCC with poorly differentiated or basaloid features has recently been recognized as a new clinical entity with a different etiology and prognosis. Nonoropharyngeal BSCC appears to share etiologic factors, genetic alterations and an immunoprofile with conventional SCC of the upper aerodigestive tract. However, the divergent differentiation of BSCC into various non-basaloid, epithelial or mesenchymal elements suggests the participation of more mulipotential cells than in SCC. The biologic behavior of BSCC has been reported to be worse than or equal to that of SCC, yet the data including the increasing numbers of human papillomavirus-associated cases now require reanalysis. It is presently uncertain whether BSCC is a histogenetically or clinically unique disease entity.