Acantholytic squamous cell carcinoma in upper aerodigestive tract: histopathology, immunohistochemical profile and epithelial mesenchymal transition phenotype change.

Acantholytic squamous cell carcinoma is a rare variant of squamous cell carcinoma in the mucosa of upper aerodigestive tract. Histomorphologically, acantholytic squamous cell carcinoma may lose the typical features of conventional squamous cell carcinoma and mimic other epithelial or mesenchymal malignancies due to advanced acantholysis and dyskeratosis. Because of its rarity, information of prognosis, pathologic features and immunohistochemical profiles is limited. We have studied clinicopathologic features and immunohistochemical profiles of four acantholytic squamous cell carcinoma cases arising from upper aerodigestive tract. Clinical results indicate an aggressive biologic behavior. Morphologically, all tumors revealed significant acantholysis with separation of tumor cells and intratumoral spaces. The tumor cells were highly pleomorphic and growth patterns were variable. In immunohistochemical studies, all tumor cells revealed positive reactions for AE1/AE3 and p63 supporting a squamous epithelial origin. In contrast to conventional aerodigestive squamous cell carcinoma, acantholytic squamous cell carcinoma showed significant reductions of cytokeratin19, E-cadherin and concomitant up-regulation of vimentin expression. Both morphologic features and immunohistochemical profiles indicate that acantholytic squamous cell carcinoma has acquired an epithelial mesenchymal transition phenotype. However, in contrast to other solid malignant tumors, the epithelial mesenchymal transition phenotype change in acantholytic squamous cell carcinoma is not limited to the invasive front of the peripheral tumor but, rather, diffusely involves entire neoplastic lesion. In addition, because cytokeratin 19 staining is attenuated, this would be an insensitive marker for following up and/or in detecting disseminated tumor cells in cases of acantholytic squamous cell carcinoma in upper aerodigestive tract.