[Basaloid squamous epithelial carcinoma of the mouth mucosa]

The basaloid-squamous carcinoma (BSC) that was first described in 1986 by Wain et al. for the head and neck region is a rare distinct variant of squamous cell carcinoma (SCC). The cardinal histopathologic feature is a biphasic cellular pattern of basaloid and squamous components. BSC has been confused with solid adenoid cystic carcinoma (ACC). Although the number of reported cases is small, BSC appears biologically virulent, with a propensity to aggressive local behavior, early regional and distant metastasis, and subsequent poor survival. We report the clinicopathological characteristics of 4 new cases and compare their immunohistochemical features with those of solid ACC and conventional SCC. Our results show that BSC, ACC and SCC react to CK 5/6. SCC is CK 10- and CK 13-positive, while BSC and ACC are negative for these markers. BSC and ACC react to CK 8, but in ACC only the luminal cells are CK 8 positive: therefore ACC has a glandular pattern. Our findings indicate that the immunohistochemical differences between BSC and ACC can facilitate their differential diagnosis. Because the biologic behavior of BSC differs from ACC and SCC, distinction among these tumor types is warranted.