Ultrastructural characterization of intermediate cells of mucoepidermoid carcinoma of the parotid.

Five cases of mucoepidermoid carcinoma of the parotid gland were studied ultrastructurally. In addition to epidermoid cells (tonofilament-rich) and mucous cells, three forms of intermediate cells were identified: mitochondria-rich cells, glycogen-rich cells, and ribosome-rich cells. Transitional forms of all cell types were observed. Ultrastructurally, cells rich in glycogen appeared to be the "clear cells" by light microscopy; cells rich in ribosomes appeared basophilic under light microscopy. Mitochondria-rich cells were lightly eosinophilic under light microscopy.