BREAST CANCER WITH NEUROENDOCRINE DIFFERENTIATION - THE CURRENT STATE OF KNOWLEDGE AND CLINICAL IMPLICATIONS

Abstract

Background. Breast neuroendocrine neoplasms (BNETs) represent a rare and heterogeneous subgroup of breast cancers, comprising 2-5% of all breast carcinomas. Their classification has undergone significant changes following the WHO 2019 and 2022 revisions, which redefined diagnostic criteria and introduced new subtypes. Aim. This review aims to summarise the current state of knowledge on BNETs and discuss clinical implications for practicing oncologists, with emphasis on pathomorphological features, diagnosis, treatment, and prognosis. Material and methods. A comprehensive review of the literature was conducted using PubMed. Studies published between 2010 and 2024 were included. Search terms included 'neuroendocrine breast neoplasm', 'BNET', 'neuroendocrine carcinoma breast', and 'breast NET'. Results. BNETs are classified into well-differentiated neuroendocrine tumours (NETs, G1/G2) and poorly differentiated neuroendocrine carcinomas (NECs, G3). Diagnosis requires immunohistochemical confirmation with synaptophysin and chromogranin A. Treatment follows IBC-NST guidelines, with emerging options including SSAs, PRRT, and targeted agents for PIK3CA-mutated tumours. Prognosis varies significantly between subtypes, with NECs showing 5- year survival rates of 32.2-50.5% compared to 62.4-74% for NETs. Conclusions. BNETs require multidisciplinary management. Future studies should focus on developing subtype-specific treatment protocols and validating novel diagnostic markers and therapeutic targets.