Pitfalls in the diagnosis of adrenocortical tumors: a lesson from 300 consultation cases

Summary The correct pathologic classification of adrenocortical carcinoma (ACC) is relevant to establish an early therapeutic strategy of this rare malignancy. The aim of the study was to assess the most frequent pitfalls in ACC diagnosis reviewing a large consecutive series of 300 cases with an original diagnosis or a clinical suspect of ACC, which were sent in consultation to our institution between 2004 and 2014. A major disagreement that significantly modified the clinical management of patients was recorded in 26 cases (9%). The most common pitfall (10 cases) was to distinguish ACC from pheochromocytoma and vice versa. Seven other cases diagnosed as ACC were reclassified as metastases from other primaries and primary adrenal soft tissue tumors (including 3 angiosarcomas). Finally, 5 adrenocortical adenomas were reclassified into carcinomas, and 4 ACCs were converted into adenomas. Minor disagreements were mostly related to the identification of ACC variants (up to 32% of cases of adrenocortical tumors in the present series). Moreover, more than 50% of ACC cases lacked Ki-67. In conclusion, our results indicate that, in the presence of a histologically suspected ACC, a special attention should be devoted to exclude metastatic and soft tissue tumors and pheochromocytoma (in this latter case with special reference to the oncocytic variant of adrenocortical tumors). Moreover, pathologists should be aware of the major role of Ki-67 in determining prognosis and in selecting patients to the most appropriate treatment.