Expression of proliferating cell nuclear antigen in follicular thyroid tumors: Correlation with clinicopathological findings

The purpose of this study was to correlate proliferating cell nuclear antig en (PCNA) immunostaining with clinicopathological findings in 60 follicular thyroid tumors. Mean proliferative index (PI) was significantly higher for carcinoma (73%) than microfollicular adenoma (19.6%) (p<0.0001). For atypi cal and oncocytic adenomas, intermediate PI values (64% and 50%) correlated with size and cytological atypia but not with sex and age. PCNA immunostai ning is of limited value for differential diagnosis of malignant and atypic al tumors but could be useful for identification of actively growing atypic al follicular thyroid nodules on fine needle aspiration biopsies.