Abstract
Background/Aim
Breast cancer remains the most prevalent type of cancer among women worldwide, and it remains the primary cause of cancer-related deaths in this demographic. Neuroendocrine breast cancer (NBC), an uncommon subtype comprising less than 1% of cases, typically occurs in older women and displays as a slow-growing, low-grade condition. NBC exhibits distinct histological patterns and immunohistochemical markers. Given the limited data on NBC, assays are required that will provide information on molecular profiling and assist in clinical decision making. The aim of the study was to investigate whether a modern Multigene Assay (MGA) could assist on treatment planning of NBC patients.
Case Report
A cohort of four patients was analyzed using a MGA. The presented cases featured young, pre-menopausal women with clear NBC, lacking family history. All were lymph node-negative, with robust expression of neuroendocrine markers. Despite high hormone receptor expression, all tumors were poorly differentiated with elevated Ki67 levels. Oncotype DX analysis indicated a need for chemotherapy in three cases and not in one. This underscores the heterogeneity within NBC, emphasizing the importance of personalized treatment decisions.
Conclusion
While NBC is rare and lacks extensive studies, the use of multigene assays like Oncotype DX may play a pivotal role in treatment planning, especially in cases with varying histological parameters.
Keywords: Breast cancer, neuroendocrine breast tumor, OncotypeDX, recurrence score
Breast cancer stands as the most prevalent form of cancer among women globally, and it constitutes the primary cause of cancer-related mortality in this demographic (1). Clinical practice incorporates various prognostic factors for the distant recurrence of breast cancer, regardless of treatment. These encompass clinicopathological characteristics like tumor size, grade, and the presence of metastatic axillary lymph nodes (2). Additionally, there are predictive factors guiding the selection of specific therapies. These include the presence of estrogen and progesterone receptors, which indicate the benefit of adjuvant endocrine therapy, and the expression of the human epidermal growth factor receptor 2 (HER2) protein. When HER2 is overexpressed, it signifies patients who may benefit from adjuvant anti-HER2 therapy (3).
Neuroendocrine breast cancer (NBC) constitutes approximately 1% of all breast cancer cases (4). While its exact origin remains uncertain, it may arise from either mammary gland tissue or neuroectodermic cells that migrate to the ductal system (5). This form of breast cancer is more frequently observed in older women, with its incidence rising with age. Typically, it manifests as a slow-growing, low-grade disease. Recent data indicates that when tumors are small and lack lymph node involvement, they exhibit a favorable prognosis (6). NBC is characterized by clusters of cells separated by vascularized tissue and collagenous bands, giving rise to a papillary and microglandular pattern (7). The immunohistochemical markers essential for diagnosing neuroendocrine carcinoma include the presence of chromogranin, synaptophysin, or neuron-specific enolase in at least 50% of cancer cells. According to the World Health Organization (WHO), these tumors are categorized into three primary histological patterns: solid, which are well-differentiated and have the best prognosis, small cell, and large cell (8). Morphologically, NBC resembles malignancies found in the gastrointestinal tract and lungs, although it is not commonly associated with carcinoid syndrome (7).
The initial reports of primary NBCs showed unfavorable results that were initially linked to their aggressive clinical and pathological characteristics. It's worth noting that these early reports primarily featured patients with predominantly undifferentiated tumors, low hormone receptor expression, and were in advanced stages (9-11). However, more recent findings indicate that smaller tumors without lymph node involvement generally lead to very positive outcomes. Factors, such as histological grade, presence of estrogen receptors, tumor size, nuclear grade, and lymph node status can all serve as predictors of prognosis, as seen in other types of breast cancer (6).
The Oncotype DX Breast Recurrence Score test was developed to predict chemotherapy benefit based on tumor biology by analyzing the expression of 21 genes. The genes included in the Oncotype DX Breast Cancer Assay are involved in cell proliferation (Ki-67, STK15, Survivin, Cyclin B1, MYBL2), invasion (Stromelysin 3 and Cathepsin L2), human epidermal growth factor receptor 2 (GRB7, HER2), estrogen (ER, PR, Bcl2, SCUBE2), GSTM1, BAG1, CD68 and reference genes (Beta-actin, GAPDH, RPLPO, GUS, TFRC). The expression of these genes is performed by reverse-transcription polymerase chain reaction (RT-PCR) and the results populate a proprietary algorithm that produces a score from 0-100 called the Recurrence Score (RS) (12). Oncotype DX is recommended by all international medical guidelines as the most validated multigene assay that can be used to assist in deciding whether chemotherapy should be prescribed or not in early-stage breast cancer patients. Premenopausal patients or patients younger than 50 years old with either negative lymph nodes (N0) or 1-3 positive lymph nodes (N1), with RS 0-25 have no benefit from chemotherapy. Patients ≤50 years old and N0 have a small chemotherapy benefit (~7.8%) from RS 21-25 and patients with RS 26 and above have a substantial chemotherapy benefit (13).
However, earlier research on early-stage invasive breast carcinomas has demonstrated that a 21-gene expression test furnishes supplementary predictive insights that are not reliant on clinicopathologic characteristics (14,15). Additionally, it anticipates the advantages of adjuvant chemotherapy for cases involving estrogen-receptor-positive disease. Initially, validation was carried out prospectively using preserved tumor samples from concluded studies that employed a prospective-retrospective design (14). Although this form of validation yielded Level IB of evidence, confirmation through actively conducted studies offers the most robust evidence to substantiate the clinical validity and, ultimately, the clinical applicability of a novel biomarker (16,17).
The prospective study known as Trial Assigning Individualized Options for Treatment (TAILORx) demonstrated that utilizing endocrine therapy alone was equally effective as combining adjuvant chemotherapy with endocrine therapy (chemoendocrine) in women with hormone-receptor-positive, HER2-negative, axillary node-negative breast cancer and a 21-gene recurrence score ranging from 11 to 25 (12). Given the limited knowledge available on this type of cancer, which is supported mainly by a small number of case reports, our aim was to present a group of four patients who underwent additional analysis using a modern molecular genetic analysis to contribute to the existing database for this exceptionally rare form of tumor.
Case Report
We present 4 patients with clear NBC treated in the Breast Unit of the Athens Medical Center during the last three years. They were all young, pre-menopausal women with no family history of breast cancer. All cases were lymph node-negative by sentinel lymph node biopsy (SLNB) and all tumors have shown clear immunohistochemical characteristics of Neuroendocrine Breast Cancer; they all had strong expression of Chromogranin and strong expression of Synaptophysin by immunohistochemistry (Figure 1).
Figure 1. Hematoxylin and Eosin and immunohistochemistry staining of one of the cases. (A, B): Hematoxylin and Eosin staining of one of the cases (magnification ×4 and ×10 respectively) showing solid and trabecular nests of neoplastic cells in a fibrous stroma. (C, D): Immunohistochemistry staining (magnification ×4 and ×20 respectively) is showing strong expression of chromogranin (C) and synaptophysin (D).
All tumors had high expression of hormone receptors and they were all HER2-negative; however, they were all poorly differentiated and had a high Ki67 expression. Due to combination or high expression of hormone receptors and high risk immunohistochemical characteristics, we evaluated the tumor formalin fixed paraffine embedded (FFPE) tissues with Oncotype DX and the Recurrence Score was high (>25) in three of them, indicating worse prognosis and need of Chemotherapy (16) and low (<25) in one, indicating good prognosis and no chemotherapy benefit. Tumor size, SLNB status and immunohistochemical evaluation, as well as OncotypeDX Recurrence Score for each case, is shown in Table I.
Table I. Clinical data and immuno-histochemical characteristics of the tumors.
ER: Estrogen receptor; PR: progesterone receptor; SLN: sentinel lymph node; RS: OncotypeDX recurrence score; ER/PR score >50: Positive (300=maximum value).
Discussion
Neuroendocrine breast cancer (NBC) is an uncommon variety of breast cancer, comprising less than 1% of all breast cancer cases (4). It is more commonly observed in older women and typically manifests as a low-grade, slowly progressing condition (6). However, in our cohort it was found in younger women and with mixed biological characteristics; although tumors were of high nuclear Grade and Ki67 proliferation index, they all had strong ER-positive expression.
Initial reports of primary breast NBCs showed unfavorable outcomes that were attributed to their aggressive nature. However, these early reports predominantly featured poorly-differentiated tumors, with low expression of hormone receptors and were at an advanced clinical stage (9-11). Subsequent investigations highlighted the effectiveness of treatment plans when the diagnosis was established early in the clinical process (18,19). The data underscore that if these tumors are small and do not involve the lymph nodes, outcomes are typically very positive. Factors, such as histological grade, presence of estrogen receptors, tumor size, nuclear grade, and lymph node status consistently serve as reliable predictors of prognosis (6).
In a literature review, we were able to identify only few case reports of NBCs (around 100 cases) that differed greatly regarding their age, grade, size and overall prognosis thus, the management of these patients was not clear. In addition to this, there were no prospective studies that can enlighten us on the management of this cohort of patients. For this reason, we decided to use a multigene assay to guide treatment decisions for these patients, determine their prognosis and see if there are any NBC patients that can be spared chemotherapy.
Based on data from the prospective clinical trial TAILORx that all international oncology guidelines are using in order to recommend the use or omission of chemotherapy 75% (3/4) of the patients had an RS higher than 25 and thus chemotherapy is recommended and 25% of them (1/4) had a low RS and thus in that patient chemotherapy can potentially be omitted (12). Our data showed that the Recurrence Score confirms the mixed prognosis of Neuroendocrine Breast Cancers and can be a useful tool to determine the risk that these patients will appear with a distant recurrence and whether they are gaining an advantage from the inclusion of chemotherapy in their treatment plan. Since our cohort of patients exclusively includes patients with no nodal involvement, one can speculate that even with N0 disease the prognosis of these patients is poor, in contrast with the literature that concludes that nodal status is an adverse prognostic factor (6).
Triple-negative breast cancer (TBNC) is a heterogenous disease that due to its aggressive behavior and lack of effective targeted therapies, justifies the need for identification of new biomarkers that will decide towards the chemotherapy treatment option (20). Cell adhesion regulates tumorigenesis and new blood vessel formation. Therefore, identifying effective targets for TBNC and cell adhesion could reveal new therapeutic approaches. Recently, a study on differentially expressed genes in the biological process of cell adhesion network between TBNC and normal cancer free tissues shed light on new potential gene candidates, revealing that mRNA-miRNA-lncRNA interactions could play a role in TNBC development (21).
Study limitations. A greater number of patients and longer follow-up is required. Additionally, although there are no specific data for the Oncotype DX panel on this rare type of tumor, it seems that multi-gene assays in general and specifically Oncotype DX may play a key role on deciding the treatment planning in patients with this rare tumor type but with heterogeneity in histologic parameters.
Conclusion
Patients in this cohort were of mixed prognosis according to their OncotypeDX RS result, although they all had a high Grade and a high (>20%) Ki67 score, which makes it difficult to identify a cohort of patients that can be safely spared chemotherapy without the use of a multigene assay.
Conflicts of Interest
The Authors have no conflicts of interest to declare in relation to this study.
Authors’ Contributions
CM, NT, KA, EK: Data collection, analysis, interpretation, drafting, editing, revision; NT: conception, oversight, editing, revision.
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