Breast neuroendocrine neoplasms: practical applications and continuing challenges in the era of the 5th edition of the WHO classification of breast tumours

Abstract The classification and nomenclature for breast neuroendocrine neoplasms have undergone several iterations. The most recent (5th) edition of the World Health Organization (WHO) classification of breast tumours defines pure primary neuroendocrine neoplasms into neuroendocrine tumour (NET) and neuroendocrine carcinoma (NEC), in alignment with other organ systems, and segregates other lesions that exhibit neuroendocrine morphology/markers into alternative categories. This review will provide an update of the nomenclature evolution, diagnostic criteria and ancillary studies, and prognostic and clinical management of breast neuroendocrine neoplasia, focusing on a practical approach and highlighting remaining issues in this field.