Proliferating cell nuclear antigen immunohistochemistry in epithelial-myoepithelial carcinoma of the salivary glands.

Myoepithelial-type cells are largely predominant in the composition of aggressive recurrent epithelial-myoepithelial carcinoma, suggesting that such tumor cell lineage constitutes a highly proliferating neoplastic population. Thirteen cases of epithelial-myoepithelial carcinoma, seven of the solid type and six of the tubular-cribriform type, were immunostained with the anti-proliferating cell nuclear antigen PC10 antibody to evaluate the proliferative activity of the two tumor cell components. Positively stained nuclei were only observed in the myoepithelial cells. Only one of the 13 cases, of tubular architectural type, had a few but unequivocally positive ductlike cells. The percentage of cycling clear cells varied between 0.2% and 45.7%. Higher values were observed in the solid (11.2% to 45.7%) as compared with tubular-cribriform epithelial-myoepithelial carcinoma (0.2% to 6.3%) and were associated with a high recurrence rate of the neoplasm. No other relationship was found between proliferating cell nuclear antigen indexes and clinical evolution. These results point to epithelial-myoepithelial carcinoma growth being related to the proliferation of the myoepithelial cell component. The proliferating role of the duct cell population seems to be irrelevant, which points to these neoplastic cells being a "terminally differentiated" component with low potential dividing capacity.