Diagnostic impact of 18F-FDG PET/CT on the management of rare breast carcinomas: Apocrine and neuroendocrine carcinomas

Retrospective literature review of primary neuroendocrine neoplasms of the breast (BNEN) in 209 Chinese patients: Treatment and prognostic factor analysis

Background

The prognostic factors and optimal choice of treatment for primary neuroendocrine neoplasms of the breast (BNEN) remain to be defined.

Methods

Patients diagnosed with BNEN in China were retrospectively reviewed from the literature following the systematic search of China National Knowledge Infrastructure (CNKI), Chinese biomedical literature service system (sinomed), wanfang medical network, and Pubmed database. The clinical characteristics and different treatment modalities of patients with BNEN were evaluated.

Results

A total of 209 cases with BNEN were enrolled. There were 204 female and 5 male patients. The median age was 51 years old (range, 17–82). Out of 209 patients with BNEN, 208 (99.5%) patients were treated with surgery (SG), 44 patients (21.1%) had received radiotherapy (RT), 173 patients (82.8%) experienced chemotherapy (CT). A total of 158 patients with hormone receptor (HR) positive (87.8%, 158/180) were treated with endocrine treatment (ET). The median follow-up time was 52.4 months (range, 6–144). The 3-year overall survival (OS) rate and 3-year disease-free survival (DFS) rate for the whole group were 93.7% and 85.3%, respectively. In univariate analyses, Ki67 expression ≥20%, HR negative, neuroendocrine carcinomas (NECs) were associated with decreased OS and DFS (P < 0.05). Patients treated with anthracycline/taxane-containing CT regimens, or taxane-containing CT regimens had superior OS and DFS than patients without those (P < 0.05). Among 69 patients with stage I who received CT had no significant differences in OS or DFS compared to those without CT. Multivariate Cox regression analysis showed that gender, HR expression, pathologic subtype, and CT were independent prognostic factors for DFS but not OS (P > 0.05).

Conclusions

The best selection of patients to get the most benefit from different treatment modalities warrant further exploration. The clinicopathological parameters including gender, HR expression, ki67 expression, pathologic type, stage, tumor size, and lymph node status may serve as both indicators of diagnosis and prognosis, and guide treatment decisions for BNEN.

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Surgery is a cornerstone of BNEN.

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ET may have a long-term superior effect on patients with HR-positive.

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Low-risk BNEN patients may be spared CT and managed with ET.

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Many clinicopathological parameters were very important for BNEN.

Neuroendocrine Neoplasms of the Breast: The Latest WHO Classification and Review of the Literature

Simple Summary

Breast tumors exhibiting neuroendocrine differentiation are a heterogeneous group of tumors that have been variously defined in previous World Health Organization (WHO) classifications. In the WHO Classification of Tumours, 5th edition, neuroendocrine tumors (NETs) and neuroendocrine carcinomas (NECs) of the breast, both of which are invasive cancers, are classified as neuroendocrine neoplasms (NENs) of the breast. However, the clinical significance of NE differentiation in breast cancers, especially in NETs of the breast, is not yet fully understood, and a large overlap appears to exist between breast cancers showing NE differentiation and invasive breast cancer of no special type (IBC-NST). While breast NECs show distinct clinical and morphological features, diagnosis of NETs based on the morphological characteristics alone can be challenging; one reason is that breast NETs do not necessarily have the same morphological characteristics as those of NENs arising in other organs. Thus, the heterogeneity of breast tumors with neuroendocrine differentiation and the changes in their classifications over the years have left many open issues that still need to be resolved. In this review, we shall summarize the history of breast “NENs,” including of mixed types of tumors and the characteristics of these tumors, and discuss their differences from NENs arising in other organs.

Abstract

Breast tumors with neuroendocrine (NE) differentiation comprise an uncommon and heterogeneous group of tumors, including invasive breast cancer of no special type (IBC-NST) with NE features, neuroendocrine tumors (NETs), and neuroendocrine carcinoma (NEC). The most recent World Health Organization (WHO) classification in 2019 defined neuroendocrine neoplasms (NENs) of the breast (Br-NENs) as tumors in which >90% of cells show histological evidence of NE differentiation, including NETs (low-grade tumors) and NEC (high-grade). Due to the low prevalence of these tumors and successive changes in their diagnostic criteria over the years, only limited evidence of these tumors exists, derived mainly from case reports and retrospective case series. Breast tumors with NE differentiation are usually treated like the more commonly occurring IBC-NSTs. Immunohistochemistry (IHC) of breast tumors with NE differentiation usually shows a hormone receptor (HR)-positive and human epidermal growth factor type 2 (HER2)-negative profile, so that hormonal therapy with cyclin-dependent kinase (CDK)4/6 inhibitors or other targeted agents would be reasonable treatment options. Herein, we present a review of the literature on breast tumors with NE differentiation as defined in the latest WHO 2019 classification, and discuss the clinical management of these tumors.

Neuroendocrine Cancer of the Breast: A Rare Entity

Neuroendocrine breast cancer (NEBC) is a rare histotype of breast carcinoma that presents, in most cases, positive hormone receptors and negative HER2. Indeed, the analysis of gene expression profiles revealed that NEBC belongs mainly to the luminal subtype. Cases of HER2-positive and triple-negative NEBC are rare. The cardinal treatment of early NEBC is surgery, similar to the treatment of invasive non-special histological type carcinoma. The use of radiotherapy follows the criteria applied in infiltrating breast cancer of non-special histotype. In the post-operative phase, therefore after the surgical treatment of mammary quadrantectomy, or mastectomy associated with homolateral sentinel lymph node removal ± axillary dissection, based on the histopathological characteristics of the tumor, the use of chemotherapy (anthracycline + taxane) and/or hormone therapy, whether or not associated with anti-HER2 therapy (trastuzumab) is the rule. Literature data report the use of cisplatin and etoposide, as in small cell lung cancers. Most of the information currently available derive from single case reports or a series of clinical cases; it follows the difficulty of formulating definite recommendations on the correct management of this histological type of breast cancer. This review describes available knowledge on this rare entity to improve the diagnostic and therapeutic strategies and offer insights to stimulate exploration of the many aspects still unknown.