Primary Neuroendocrine Neoplasms of the Breast: Still Open Issues

Abstract

Neuroendocrine breast tumors represent a rare subtype of breast cancer, accounting for less than 1% of all neuroendocrine neoplasms. Starting from their pathology definition, and going through their prevalence, prognosis and treatment, our knowledge is still really uncertain. In the present short review of the medical literature on this topic, we have evaluated in details their epidemiology, risk factors, pathogenesis, pathology, clinical presentation, radiographic aspects, prognosis, and therapy. We have thus been able to identify a number of open issues regarding primary neuroendocrine neoplasms of the breast that need to be clarified. Our ultimate aim was actually to try to understand whether neuroendocrine neoplasms of the breast can be considered a definite clinical entity and if neuroendocrine differentiation of breast tumors has a really clinical relevance.

Five‐year outcomes in patients treated with surgery and radiotherapy for primary neuroendocrine neoplasm of the breast

“…BNEN represents less than 1% of all breast cancers and less than 1% of all neuroendocrine tumors. 1 The lack of large-scale trials makes establishment of consensual treatment recommendations difficult, and no guidelines have been published for this histologic subtype to this date. As a matter of fact, the usual management of nonmetastatic BNEN is still empirically based on the standard of care for ductal invasive carcinomas: while surgery is systematic, neo-adjuvant, or adjuvant treatments are based on clinical, pathological, and histological considerations.…”

“…11 Finally, most of our patients expressed hormonal receptors; in this context, hormonal therapy could be logically recommended. 2 It has been proposed that BNEN derived from the same cancer stem cell population as invasive ductal carcinomas (IDC), 1,12 which might explain the frequent co-existence of neuroendocrine and epithelial populations, the frequent expression of hormonal receptors and common genomic characteristics between BNEN and IDC. 13 This advocates for the same chemotherapy regimens as for ductal invasive carcinomas and suggests that BNEN could be conceptually close to prostate adenocarcinomas acquiring a neuroendocrine differentiation associated with the development of hormone castration resistance.…”

“…Primary breast neuroendocrine neoplasms (BNEN) represent less than 1% of all breast carcinomas. 1 This terminology refers to a heterogeneous group of breast tumors characterized by specific biological, histological, and prognostic characteristics, 1 recognized by the World Health Organization (WHO) as a distinct entity of breast cancer. Their definition, prevalence, and prognosis remain, however, controversial, 2 and due to their rarity, most information sources on BNEN management consist of case reports and limited retrospective case series.…”

Neuroendocrine Breast Cancer. Clinical Observation. Personalized Approach

“…Neuroendocrine breast tumors represent a rare subtype of breast cancer, accounting for less than 1 % of all neuroendocrine neoplasms. Starting from their pathology definition, and going through their prevalence, prognosis and treatment, our knowledge is still really uncertain [2]. The morphological diagnosis of breast NET is a problem not only for novice pathomorphologists, but even for experts.…”

“…In the more recent WHO classification published in 2019, BNEN can only be identified only when the proportion of neuroendocrine cells in samples is greater than 90 % [9]. BNEN are overall heterogeneous in their definition, being characterized by a various grade of differentiation and histological overlap, and at present, they do not identify a definite clinical entity, and no specific prognosis or therapy have been recognized yet [2]. At the present moment, the problem of diagnosing and treating NET in Russia is in the lack of statistical data on the morbidity and mortality caused by this pathology, the lack of doctors' knowledge (oncologists, surgeons, endocrinologists, gastroenterologists) about the features of diagnosis, clinical course, principles of antitumor treatment and the lack of possibility or inaccessibility of IHC confirmation [10].…”