This review encompasses the diagnostic features of malignancy, the routinely observable prognostic features and the prognostic and predictive features emerging from research techniques in the principal endocrine neoplasms: pancreatic and extrapancreatic endocrine cell tumours, thyroid and parathyroid neoplasia, adrenal cortical neoplasms and adrenal and extra-adrenal paragangliomas. While each endocrine tissue has its own set of diagnostic features for malignancy, and prognostic features once a diagnosis of malignancy has been established, there are a few common themes. For several endocrine neoplasms, definite recognition of malignancy can be difficult and may depend upon frank invasive or metastatic growth at presentation. Endocrine tissues are dynamic, with hyperplastic and regressive phenomena, some of which may mimic malignancy. Even when unequivocal features of malignancy are available for observation, their distribution in tissue may be very focal, necessitating thorough sampling. The accurate documentation of routinely observable histological features interpreted in the light of current literature has not been superseded by special techniques in the statement of diagnosis or prognosis in the vast majority of endocrine neoplasms.