Clear cell carcinoma: review of its histomorphogenesis and classification as a squamous cell lesion.

In current classification schemes, clear cell carcinoma-including both the hyalinized and nonhyalinized variety--is now an accepted subtype of malignant salivary gland tumors. Despite this, the underlying cellular differentiation process leading to the typical histomorphology of this neoplasm remains unclear. This review summarizes and illustrates the histologic, ultrastructural, and immunohistochemical evidence for the underlying squamous cell nature of clear cell carcinoma. Squamous cell differentiation is not an uncommon feature of nonneoplastic and neoplastic lesions of the salivary glands. Clear cell carcinoma needs to be added to this list as a unique but specific variety of clear cell squamous carcinoma.