Abstract
No reliable pathologic criteria have been identified that predict clinical behavior in adrenal and extra-adrenal pheochromocytomas (PHEOs). Reliable prognostic markers for the prediction of clinical outcome are needed to assign optimal treatment for potentially malignant tumors. In this report, we evaluated several molecular markers (topoisomerase II alpha, E-cadherin, HER-2/neu, and retinoblastoma (RB) gene protein) that have not been previously studied in PHEOs. Paraffin-embedded, formalin-fixed tissue blocks from 50 cases of PHEO (30 benign and 20 malignant, 31 adrenal and 19 extra-adrenal) were obtained from University of Utah Health Sciences Center, Salt Lake City, and the Medical College of Wisconsin, Milwaukee. Gross (tumor size, weight, local extension, cyst formation, hemorrhage, necrosis), microscopic (pleomorphism, hyaline globules, intranuclear inclusion, mitotic count, capsular and vascular invasion, ganglionic/neuronal differentiation), and immunohistochemical features (topoisomerase II alpha, p53, MIB-1, E-cadherin, RB, and HER-2/neu) were studied. With the exception of vascular invasion (P = 0.025), there were no unequivocal gross or microscopic characteristics that distinguished benign from malignant lesions (P ≅ 0.11–0.71). Topoisomerase II and MIB-1 indices in malignant lesions were significantly higher than those observed in benign lesions (P = 0.012 and 0.019). Differences in p53 expression were not statistically significant (P = 0.082). Loss in RB protein product expression was significantly more common in malignant lesions (P = 0.001). E-cadherin loss and HER-2/-neu overexpression were not observed in any of the benign or malignant lesions. We studied the immunohistochemical expression of topoisomerase II alpha, MIB-1, p53, RB gene protein product, E-cadherin, and HER-2/neu in a series of adrenal and extra-adrenal PHEOs. Overexpression of topoisomerase II alpha and MIB-1 and loss of RB protein product were more common in malignant lesions, whereas p53, E-cadherin, and HER-2/neu do not seem to have diagnostic utility in the prediction of biologic behavior in these neoplasms.
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