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

Jonasz Żuk; Kinga  Bukała; Szymon Klimaszewski; Mikołaj  Daniluk; Zuzanna Wiktoria  Szumska; Mateusz Onopiuk; Jowita Wiktoria Maksymiuk; Urszula  Gadomska; Natalia  Dejewska; Aleksandra Greluk

doi:10.31435/ijitss.3(51).2026.6180

Authors

Jonasz Żuk The University Clinical Center of Medical University of Warsaw, Poland https://orcid.org/0009-0001-7500-7982
Kinga Bukała Medical University of Lodz, Lodz, Poland https://orcid.org/0009-0003-9587-4826
Szymon Klimaszewski Praktyka lekarska dentystyczna Józefa Czyżewskiego 32b lok. 3, 80-336 Gdańsk, Poland https://orcid.org/0009-0001-3505-2797
Mikołaj Daniluk The University Clinical Center of Medical University of Warsaw, Poland https://orcid.org/0009-0005-6458-373X
Zuzanna Wiktoria Szumska District Hospital in Otwock, Poland https://orcid.org/0009-0009-5287-9946
Mateusz Onopiuk Bielański Hospital named after Rev. Jerzy Popiełuszko, Warsaw, Poland https://orcid.org/0009-0003-9916-1292
Jowita Wiktoria Maksymiuk Bielański Hospital named after Rev. Jerzy Popiełuszko, Warsaw, Poland https://orcid.org/0009-0004-3130-9913
Urszula Gadomska Bielański Hospital named after Rev. Jerzy Popiełuszko, Warsaw, Poland https://orcid.org/0009-0005-8381-9955
Natalia Dejewska Bielański Hospital named after Rev. Jerzy Popiełuszko, Warsaw, Poland https://orcid.org/0009-0006-4806-6780
Aleksandra Greluk Medical University of Lublin, Lublin, Poland https://orcid.org/0009-0004-5158-1930

DOI:

https://doi.org/10.31435/ijitss.3(51).2026.6180

Keywords:

Breast Cancer, Neuroendocrine Neoplasm, Neuroendocrine Tumour, Neuroendocrine Carcinoma, Immunohistochemistry, WHO Classification

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.

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