Clear cell tumors of the salivary glands, jaws, and oral mucosa.

Clear cell tumors of the oral mucosa, jaws, and salivary glands constitute a heterogeneous group of lesions which may be either odontogenic, salivary gland, or metastatic in origin. Clear cells in these proliferations most frequently result from fixation artifact but may also be the result of cytoplasmic accumulation of water, glycogen, intermediate filaments, or immature zymogen granules, or a paucity of cellular organelles. Odontogenic neoplasms that may be characterized by a predominantly clear cell component include odontogenic carcinoma, ameloblastoma, and calcifying epithelial odontogenic (Pindborg) tumor. Clear cell tumors of salivary gland origin are almost invariably malignant in nature but they do include two benign lesions; namely, oncocytoma and myoepithelioma. Clear cells in acinic cell carcinoma seldom comprise a significant portion of the tumor whereas clear cell mucoepidermoid carcinomas can readily be identified by an admixture of clear-squamoid, mucous and intermediate cells. Lesions previously reported as "clear cell adenoma" "clear cell carcinoma, or glycogen-rich carcinoma" can be divided into the distinctive biphasic epithelial-myoepithelial carcinoma and monophasic lesions which have been shown to be either myoepithelial or ductal in origin. The latter are primarily represented by the recently described "hyalinizing clear cell carcinoma." The most common metastatic clear cell tumor in the oral mucosa and the jaws is the renal cell carcinoma. However, metastases of melanoma and malignant clear cell tumors of the prostate, bowel, thyroid, and liver must also be considered.