Anti-CD10 (56C6) is expressed variably in adrenocortical tumors and cannot be used to discriminate clear cell renal cell carcinomas

In the evaluation of retroperitoneal masses, the practicing pathologist faces a dilemma when making a diagnosis based on histology given the often overlapping morphologic appearances of the adrenocortical carcinoma, renal cell carcinoma (RCC), and hepatocellular carcinoma (HCC). CD10 is expressed in a membranous fashion in the vast majority of clear cell RCCs; therefore, it is widely used for distinction from its mimics. However, its expression is not well-investigated in adrenal cortical tumors. We examined CD10 expression in 47 surgically resected adrenocortical tumors (26 adenomas and 21 carcinomas) and compared with 20 clear cell RCCs and 25 HCCs. Twenty HCCs (80%), 18 RCCs (90%), 11 adrenocortical carcinomas (52%), and 18 adrenocortical adenomas (69%) were positive for CD10. HCCs were characterized by a canalicular staining, and clear cell RCCs exhibited membranous or mixed membranous-cytoplasmic staining. Adrenocortical tumors displayed mainly cytoplasmic staining. Four adrenocortical carcinomas and one adenoma also displayed the membranous staining pattern. Despite the relatively small number of samples, our preliminary results revealed that adrenocortical tumors may express CD10 (Clone: 56C6). The most important point from this paper is the fact that anti-CD10 expression has not been previously reported in adrenocortical carcinomas. This suggests that CD10 does not seem to be a useful marker for discriminating clear cell RCCs from adrenocortical tumors since CD10 expression does not rule out the possibility of adrenocortical tumors. This feature should be kept in mind when constructing an antibody panel for an epithelial tumor that involves the adrenal gland and kidney, especially in small biopsy specimens.