[Interpretation of the 5th edition WHO classification of adrenal cortical tumors].

Non-neoplastic lesions were added in the 5th edition WHO classification of adrenal cortical tumor based on the recent update, including adrenal rests, adrenal cysts, congenital adrenal hyperplasia and adrenocortical nodular disease. A range of tumor concepts were updated or refined based on tumor cell origin, histopathology, oncology and molecular biology. The most significant nomenclature change in the field of adrenal cortical pathology involves the refined classification of adrenal cortical nodular disease, which now includes sporadic nodular adrenocortical disease, bilateral micronodular adrenal cortical disease, and bilateral macronodular adrenal cortical disease. The 5th edition WHO classification endorses the nomenclature of the HISTALDO classification to help the classification of aldosterone producing adrenal cortical lesions, which uses CYP11B2 immunohistochemistry to identify functional sites of aldosterone production. The 5th edition WHO classification does not change the Weiss and Lin-Weiss-Bisceglia histopathologic criteria for diagnosing adrenal cortical carcinomas, and underscores the diagnostic and prognostic impact of angioinvasion in these tumors. Reticulin algorithm and Helsinki scoring system were added to assist the differential diagnosis of adrenal cortical neoplasms in adults. Pediatric adrenal cortical neoplasms are assessed using the Wieneke system. The 5th edition WHO classification places an emphasis on an accurate assessment of tumor proliferation rate using both the mitotic count (mitoses per 10 mm2 ) and Ki-67 labeling index which play an essential role in the dynamic risk stratification of affected patients. This review highlights advances in knowledge of histological features, ancillary studies, and associated genetic findings that increase the understanding of the adrenal cortex pathologies in the 5th edition WHO classification.