[The significance of Ki-67 antigen expression in the distinction between benign and malignant pheochromocytomas].

Objectives: To investigate the expression of Ki-67 antigen in benign and malignant pheochromocytomas, and to evaluate whether the expression of Ki-67 antigen could serve as a diagnostic marker for predicting the biological behaviour of these tumors.

Methods: Ki-67 antigen were detected by immunohistochemical technique and image analysis in 57 cases of clinically documented benign and malignant pheochromocytomas were analyzed. Aside from histological study, Ki-67 immunohistochemistry studies were performed to get the Ki-67 index. Statistical analysis was performed between these groups.

Results: Ki-67 index was low in benign pheochromocytomas (average 0.98%), and high in malignant pheochromocytomas (average 3.78%). There was statistically significant difference in expressions of Ki-67 antigen between benign and malignant pheochromocytomas. The Ki-67 index of 2 cases in benign pheochromocytomas (5.1%, 2/39) and 10 cases in malignant pheochromocytomas (55.6%, 10/18) was higher than 3%. The accuracy, sensitivity, specificity, positive predictive value and negative predictive value of Ki-67 index higher than 3% to diagnosis malignant pheochromocytomas was 82.5%, 55.6%, 94.9%, 83.3% and 82.2%. The follow-ups indicated the survival rate of patients with higher Ki-67 index was lower than those with lower Ki-67 index.

Conclusions: Ki-67 may serve as a useful marker of the biological behavior of tumors, and can provide useful information for prognosis of tumor patients. Immunohistochemical assessment of Ki-67 antigen can be useful in the differential diagnosis of malignant from benign pheochromocytomas. Ki-67 index (> 3%) is a useful marker for distinguishing benign from malignant tumors or for predicting the malignant potential of pheochromocytomas.