The fourth edition of the World Health Organization (WHO) classification of endocrine tumours contains substantial new findings for the adrenal tumours. The tumours are presented in two chapters labelled as "Tumours of the adrenal cortex" and "Tumours of the adrenal medulla and extra-adrenal paraganglia." Tumours of the adrenal cortex are classified as cortical carcinoma, cortical adenoma, sex cord stromal tumours, adenomatoid tumour, mesenchymal and stromal tumours (myelolipoma and schwannoma), haematological tumours, and secondary tumours. Amongst them, schwannoma and haematological tumours are newly documented. The major updates in adrenal cortical lesions are noted in the genetics of the cortical carcinoma and cortical adenoma based on the data from The Cancer Genome Atlas (TCGA). Also, a system for differentiation of oncocytoma from oncocytic cortical carcinoma is adopted. Tumours of the adrenal medulla and extra-adrenal paraganglia comprise pheochromocytoma, paraganglioma (head and neck paraganglioma and sympathetic paraganglioma), neuroblastic tumours (neuroblastoma, nodular ganglioneuroblastoma, intermixed ganglioneuroblastoma, and ganglioneuroma), composite pheochromocytoma, and composite paraganglioma. In this group, neuroblastic tumours are newly included in the classification. The clinical features, histology, associated pathologies, genetics, and predictive factors of pheochromocytoma and paraganglioma are the main changes introduced in this chapter of WHO classification of endocrine tumours. The term "metastatic pheochromocytoma/paraganglioma" is used to replace "malignant pheochromocytoma/paraganglioma." Also, composite pheochromocytoma and composite paraganglioma are now documented in separate sections instead of one. Overall, the new classification incorporated new data on pathology, clinical behaviour, and genetics of the adrenal tumours that are important for current management of patients with these tumours.
Keywords: Adrenal; Genetic; Pathology; Tumour; WHO.