Immunohistochemical study of the proliferative activity of pleomorphic adenoma by localization of proliferating cell nuclear antigen [PCNA]

ABSTRACT

Pleomorphic adenoma [PA] is one of the most common salivary gland tumors, it is still controversial if atypical tumor cells scattered in salivary PAs are precancerous and how carcinoma arises in PA. The present study was carried-out to investigate the proliferative activity of PA by an immunohistochemical localization of proliferating cell nuclear antigen [PCNA]. Seventeen PA cases, four adenocarcinoma cases and normal salivary tissue surrounding tumor areas in three PA cases were included in the present study, from each case two paraffin sections of 5 microns thickness were obtained, one section was stained with hematoxylin and eosin stain for histologic and morphometric study of PA cases, the other section was immunohistochemically processed to detect PCNA positive cells in the studied cases. Normal salivary tissue showed no reactivity to PCNA, all adenocarcinoma cases of the present study were reactive to PCNA. From 17 PA cases only 6 cases [35.3%] were reactive to PCNA, 50% of these cases [3 cases] were of the predominantly cellular PA pattern, 16.7% [one ease] was of the predominantly myxoid PA pattern and the remaining two cases [33.3%] were of the mixed cellular and myxoid PA Statistically significant difference of mean nuclear area [P=0.01] between cellular [116.8+/-27.6 microns] and myxoid areas [55.4+/-10.8 microns] in the studied PA cases was reported in the present study, meanwhile, no significant difference between mean nuclear areas of PA cases with reactive cells and those with no reactive cells to PCNA. From the findings of the present study it can be concluded that benign salivary PA contain actively proliferating cells as indicated by higher PCNA reactivity than that of normal salivary tissue, these actively proliferating cells were expressed mainly in cellular sheet- like areas of PA, they revealed no histopathologic or morphometric differences from non-reactive PA cells. These cells may be a source of recurrence after surgical removal of PA or may be a precursors for malignant cells leading to malignant transformation of benign PA