Quantitation and localization of cycling tumor cells in pleomorphic adenomas and myoepitheliomas: an immunohistochemical analysis.

Previous investigations have suggested that in certain salivary gland tumors only nonluminal (myoepithelial-like) tumor cells proliferate and that this may have histogenetic implications; however, no quantitative assessment of the cycling component is available. We decided, therefore, to enumerate the cycling luminal and nonluminal cells in 15 pleomorphic adenomas and six myoepitheliomas by using an antibody to proliferating cell nuclear antigen. The mean percentages of cycling luminal and nonluminal cells in pleomorphic adenomas were 2.3 +/- 1.4 and 2.4 +/- 2.3, respectively, and 2.1 +/- 0.7 of the tumor cells in myoepitheliomas. Even though duct-like structures in pleomorphic adenomas are considerably separated by more numerous nonluminal cells and, therefore, cycling cells may seem fewer, both cell types proliferate at similar rates. The results indicate that nonluminal cells are not the sole proliferative component in salivary gland tumors.