Immunohistochemical assessment of proliferative activity in adrenocortical neoplasms

Although many histologic criteria have been utilized to help distinguish benign from malignant adrenocortical tumors, it still may be difficult to assess the biologic potential of a given tumor. We evaluated 19 adenomas and 15 primary carcinomas with the avidin-biotin complex peroxidase method utilizing formalin-fixed, paraffin-embedded tissues with monoclonal antibodies for proliferating cell nuclear antigen (PC10) and Ki-67 (MIB 1) to determine if staining for these antigens could be used to help differentiate benign from malignant adrenocortical neoplasms. We also evaluated whether these markers could be used as prognostic indicators. Labeling indices for both PCNA and Ki-67 were determined by enumerating 1000 tumor cells, and expressed as a percentage of cells with nuclear staining. A PCNA and a Ki-67 score was obtained by the product of the staining intensity (0-3+) and the extent of nuclear staining, expressed as an estimate of the percentage of cells staining. Both PCNA and Ki-67 score and labeling index were correlated with mitotic counts, histologic diagnosis, and clinical outcome. Follow-up period for patients ranged from 4 months to 12 years with a mean of 25 months. Mitotic counts correlated with histologic diagnosis and clinical outcome. Both Ki-67 score and labeling index were significantly higher in malignant than in benign tumors, and correlated with mitotic counts and clinical outcome. There was a strong correlation between Ki-67 score and labeling index, indicating that Ki-67 score may be a more rapid and equally accurate method of estimating proliferative index of a tumor. PCNA score and labeling index did not correlate with histologic diagnosis or clinical outcome.(ABSTRACT TRUNCATED AT 250 WORDS)