Primary neuroendocrine carcinoma of the breast: clinical, imaging, and histologic features

Primary Neuroendocrine Carcinoma of Breast: Changing Paradigm

Neuroendocrine carcinomas are one of the most rare malignancies of the breast. Theoretically they can arise from any organ of the body, but incidence in breast is very rare. Due to the ever-changing definition of the disease, no specific therapeutic guideline is available in current literature. Currently WHO defines neuroendocrine carcinoma of breast as malignant lesions that expresses > 90% of neuroendocrine markers like synaptophysin, chromogranin A with characteristic histopathology features with exclusion of solid papillary carcinoma, and hypercellular-type mucinous carcinoma.

Primary neuroendocrine tumor of the breast: A case report

Primary neuroendocrine neoplasm of the breast (PNENB) is a rare subtype of breast cancer, accounting for <1% of all breast tumors. The morphological features of PNENB are similar to those of neuroendocrine tumors originating in the lungs or gastrointestinal system, with tumor cells exhibiting the strong expression of neuroendocrine markers, including chromogranin A and synaptophysin. Since this type of cancer was first reported, the definition, classification and diagnostic criteria of PNENB have evolved and changed. However, accurate diagnostic criteria and standard treatment guidelines are lacking. The present report describes a specific case of PNENB, which was consistent with the morphological and molecular features of other cases in most previous studies. In addition, the current body of literature on PNENB, including its development, diagnosis, molecular features, treatment and prognosis is reviewed.

Radio-pathological characteristics of primary neuroendocrine breast carcinoma: Series of 4 cases

Neuroendocrine breast cancers (NEBCs) are a rare and distinct subtype of breast tumors, characterized by their neuroendocrine differentiation. Despite accounting for less than 1% of all breast cancers, NEBCs present unique diagnostic and therapeutic challenges due to their heterogeneous nature and variable prognosis. Accurate imaging plays a crucial role in the diagnosis, treatment planning, and follow-up of NEBCs, yet remains a complex area due to the rarity of these tumors and overlapping features with more common breast cancers. We present a series of 4 cases of primary NEBC, emphasizing the imaging features and their histopathological correlations. All patients presented with breast lump. Diagnostic Mammography followed by Ultrasound was performed in each case. All 4 cases were categorized as Breast Imaging- Reporting and Data System (BI-RADS)-4. Trucut biopsy was performed and histopathological analysis revealed the diagnosis of NEBC. Patients underwent Surgery followed by Chemotherapy, Hormonal Therapy or Radiation therapy alone or in combination with each other depending upon the histopathological characteristics.

Primary Neuroendocrine Tumor of the Breast: A Case Report and Review of Current Guidelines

Primary neuroendocrine tumor of the breast is a rare subtype of breast carcinoma that most commonly affects postmenopausal women in their sixth or seventh decade of life. We report a case of a 52-year-old female who presented to our clinic with concerns about a self-palpable mass involving her left breast that had not been detected on a routine mammogram five months prior. Upon clinical exam and diagnostic workup comprising imaging, a tissue biopsy, and immunostaining, she was found to have primary high-grade neuroendocrine carcinoma of the breast with necrosis. Subsequently, management of her case involved a first-line systemic chemotherapy regimen, including carboplatin with etoposide and atezolizumab. Less than two months after beginning therapy, she had undergone three cycles but did not show any significant clinical response, requiring further workup. This case demonstrates the challenges faced with treating such a rare subtype of breast carcinoma and the necessity of documenting other similar cases for improved understanding and patient outcomes.

Imaging Features and World Health Organization Classification of Rare Breast Tumors

Breast radiologists encounter unusual lesions, which may not be well described in the literature. Previously based on histologic and molecular classifications, the World Health Organization (WHO) classification of tumors has become increasingly multidisciplinary. Familiarity with imaging features and basic pathology of infrequent breast lesions, as well as their current classification according to the WHO, may help the radiologist evaluate biopsy results for concordance and help direct the management of uncommon breast lesions. This review article provides a case-based review of imaging features and WHO histologic classification of rare breast tumors.

Neuroendocrine neoplasms of the breast: a review of literature

Primary neuroendocrine neoplasms (NENs) of the breast are characterized by neuroendocrine architectural and cytological features, which must be supported by immunohistochemical positivity for neuroendocrine markers (such as Chromogranin and Synaptophysin). According to the literature, making a diagnosis of primary neuroendocrine breast cancer always needs to rule out a possible primary neuroendocrine neoplasm from another site. Currently, the latest 2022 version of the WHO of endocrine and neuroendocrine neoplasms has classified breast NENs as well-differentiated neuroendocrine tumours (NETs) and aggressive neuroendocrine carcinomas (NECs), differentiating them from invasive breast cancers of no special type (IBCs-NST). with neuroendocrine features. The current review article describes six cases from our series and a comprehensive review of the literature in the field of NENs of the breast.

Special Types of Breast Cancer: Clinical Behavior and Radiological Appearance

Breast cancer is a complex disease that includes entities with different characteristics, behaviors, and responses to treatment. Breast cancers are categorized into subgroups based on histological type and grade, and these subgroups affect clinical presentation and oncological outcomes. The subgroup of "special types" encompasses all those breast cancers with insufficient features to belong to the subgroup "invasive ductal carcinoma not otherwise specified". These cancers account for around 25% of all cases, some of them having a relatively good prognosis despite high histological grade. The purpose of this paper is to review and illustrate the radiological appearance of each special type, highlighting insights and pitfalls to guide breast radiologists in their routine work.

[Primary Neuroendocrine Carcinoma of the Breast: A Case Report and Literature Review]

In general, neuroendocrine cancer develops in the digestive or respiratory tract, and when it is found in other organs, it is often due to metastasis. Primary neuroendocrine carcinoma of the breast occurs very rarely, and the exact clinical picture, radiological findings, treatment and prognosis are not well known. Furthermore, only a small number of literature reports have been published. Here, we report the imaging findings of primary neuroendocrine carcinoma in the breast of a 51-year-old female, along with a literature review.

A high-quality model for predicting the prognosis of breast neuroendocrine carcinoma to help clinicians decide on appropriate treatment methods: A population-based analysis

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The incidence of breast neuroendocrine carcinoma (NEC) was approximately 1.96–2.37%.

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Breast NEC had poor prognosis than breast invasive ductal carcinoma (IDC).

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Patients with breast NEC may benefit from surgery plus chemotherapy.

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Efficient models were constructed to guide the treatment of breast NEC.

Background

Breast neuroendocrine carcinoma (NEC) is a rare malignancy with unclear treatment options and prognoses. This study aimed to construct a high-quality model to predict overall survival (OS) and breast cancer-specific survival (BCSS) and help clinicians choose appropriate breast NEC treatments.

Patients and methods

A total of 378 patients with breast NEC and 349,736 patients with breast invasive ductal carcinoma (IDC) were enrolled in the Surveillance, Epidemiology, and End Results (SEER) database between 2010 and 2018. Propensity score matching (PSM) was performed to balance the clinical baseline. Prognostic factors determined by multivariate Cox analysis were included in the nomogram. C-index and calibration curves were used to verify the performance of the nomogram.

Results

Nomograms were constructed for the breast NEC and breast IDC groups after PSM. The C–index of the nomograms ranged from 0.834 to 0.880 in the internal validation and 0.818–0.876 in the external validation, indicating that the nomogram had good discrimination. The risk stratification system showed that patients with breast NEC had worse prognoses than those with breast IDC in the low-risk and intermediate-risk groups but had a similar prognosis that those in the high-risk group. Moreover, patients with breast NEC may have a better prognosis when undergoing surgery plus chemotherapy than when undergoing surgery alone or chemotherapy alone.

Conclusions

We established nomograms with a risk stratification system to predict OS and BCSS in patients with breast NEC. This model could help clinicians evaluate prognosis and provide individualized treatment recommendations for patients with breast NEC.

Primary Neuroendocrine Tumor of the Breast: Current Understanding and Future Perspectives

Primary neuroendocrine carcinoma of the breast (NECB) is characterized with heterogeneity, rarity, and poor differentiation, which is probably an underestimated subtype of breast cancer, including small cell NECs and large cell NECs. The diagnostic criteria for NECB have been constantly updated as the disease changes and the understanding increases. According to the latest WHO Classification, primary neuroendocrine neoplasm (NEN) of the breast consists of well-differentiated neuroendocrine tumors (NET), extremely aggressive neuroendocrine carcinomas (NEC) as well as invasive breast cancers of no special type (IBCs-NST) with neuroendocrine differentiation. The accurate diagnosis of NECB remains a challenge for its low incidence, which needs multi-disciplinary methods. For the rarity of the disease, there is a lack of large samples and prospective clinical research. For these invasive tumors, there are no standardized therapeutic guidelines or norms, and the treatment often refers to nonspecific breast cancer. In addition, the prognosis of such patients remains unknown. In 2003, the World Health Organization (WHO) listed NECB as an independent entity for the first time, while few features of NECB were clarified. In this review, it presents the WHO Classification, clinicopathologic characteristics, diagnosis, treatment, and prognosis of these patients. In addition, it summarizes the latest studies on molecular features of NECB, aiming to provide new therapeutic perspectives for the disease.

Invasive Breast Carcinoma with Neuroendocrine Differentiation: A Single-Center Analysis of Clinical Features and Prognosis

Introduction Invasive breast cancer with neuroendocrine differentiation is a rare subtype of breast malignancy. Due to frequent changes in the definition of these lesions, the correct diagnosis, estimation of exact prevalence, and clinical behaviour of this entity may be challenging. The aim of this study was to evaluate the prevalence, clinical features, and outcomes in a large cohort of patients with breast cancer with neuroendocrine differentiation.

Patients Twenty-seven cases of breast cancer with neuroendocrine differentiation have been included in this analysis. Twenty-one cases were identified by systematic immunohistochemical re-evaluation of 465 breast cancer specimens using the neuroendocrine markers chromogranin A and synaptophysin, resulting in a prevalence of 4.5%. A further six cases were identified by a review of clinical records.

Results Median age at the time of diagnosis was 61 years. 70% of patients had T2 – 4 tumors and 37% were node-positive. The most common immunohistochemical subtype was HR-positive/HER2-negative (85%). 93% were positive for synaptophysin and 48% for chromogranin A. Somatostatin receptor type 2A status was positive in 12 of 24 analyzed tumors (50%). Neuroendocrine-specific treatment with somatostatin analogues was administered in two patients. The 5-year survival rate was 70%.

Conclusions Breast cancer with neuroendocrine differentiation is mostly HR-positive/HER2-negative and the diagnosis is made at a higher TNM stage than in patients with conventional invasive breast carcinoma. Moreover, breast cancer with neuroendocrine differentiation was found to be associated with impaired prognosis in several retrospective trials. Due to somatostatin receptor 2A expression, somatostatin receptor-based imaging can be used and somatostatin receptor-targeted therapy can be offered in selected cases.

Primary neuroendocrine carcinomas of the breast and neuroendocrine differentiated breast cancers: Relationship between histopathological and radiological features

PURPOSE

The aim of this study wasto investigate whole-breast imaging findings (mammography, ultrasonography (US), magnetic resonance imaging (MRI),clinical, and histopathological findings of primary neuroendocrine carcinomas of the breast (NEC) and neuroendocrine differentiated breast cancers (NEBC).

METHODS

Patients withadiagnosis of breast cancer with histopathological neuroendocrine features between the years 2010 and 2021 were retrospectively screened.The lesions were divided into two main groups depending on staining with neuroendocrine markers (synaptophysin and chromogranin A). Those showing focal staining were categorized as NEBC while those with diffuse staining as NEC.The mammography, US, and MRI of the lesionswere reviewed in consensus by two breast radiologists in order to assess imaging featuresretrospectively according to the Breast Imaging Reporting and Data System (BI-RADS) 5th lexicon.The findings were compared with breast cancers without neuroendocrine features (BC-WNE) which were randomly selected from the same database.

RESULTS

A total of 105 lesions [NEBC (n = 44), NEC(n = 11), BC-WNE (n = 50)] were evaluated.Patients with neuroendocrine tumors were older (p < 0.001) than those with BC-WNE. Compared with BC-WNE tumors, radiological findings typical of malignancy such as irregular shape [NEBC (7/20); NEC(3/7) vs BC-WNE (35/43); p < 0.001], spiculation [NEBC (2/20); NEC(0/7) vs BC-WNE (21/43); p < 0.001], architectural distortion [(NEBC (3/24); NEC(0/9) vs BC-WNE (31/50); p < 0.001)], calcification [(NEBC (6/24), NEC(0/9) vs BC-WNE (n = 27/50); p = 0.001)] on mamography, non-parallel orientation to skin [(NEBC (n = 17/29), NEC(n = 4/9), BC-WNE (n = 35/42); p = 0.008)], acoustic shadowing [(NEBC (n = 12/29), NEC(1/9), BC-WNE (n = 29/42); p = 0.009)], axillary lymphadenopathy [(NEBC(n = 3/30), NEC(n = 1/9), BC-WNE (21/50); p < 0.001)]on US were less common features of the neuroendocrine carcinomas of breast. Aside from shape features, there was no significant difference in contrast pattern (p = 0.866), kinetic curve (p = 0.454) and diffusion restriction (p = 0.242) on MRI.

CONCLUSION

Characteristic malignant imaging features, including irregular shape, spiculated margins, suspicious calcifications, and posterior acoustic shadowing, are uncommon in neuroendocrine carcinomas of breast. These carcinomas tend to show more benign imaging features when compared with BC-WNE.

Mammographic, Sonographic, and MRI Features of Primary Neuroendocrine Carcinoma of the Breast: A Case Report

Primary neuroendocrine carcinomas of the breast are a rare, distinct category of breast carcinomas that require immunohistochemical staining for diagnosis. Currently, there is not enough evidence on the clinical pattern, prognosis, and proper management of the disease. Only few case series have described the imaging findings of neuroendocrine carcinomas of the breast. We herein present a case of a primary neuroendocrine carcinoma of the breast (small cell) presenting as a locally aggressive tumor with metastatic disease, and describe the radiologic findings.

Primary neuroendocrine carcinoma of the breast: a rare presentation and review of the literature

Primary neuroendocrine carcinoma of the breast (NEBC) is a very rare occurrence accounting for less than 0.1% of all breast cancers. Typically, the tumor presents with ER- and PgR-positive and HER-2-negative status. Despite its luminal type, NEBC is associated with a more aggressive clinical course and poorer prognosis compared to the other types of invasive breast cancer. Clinical and radiological findings are nonspecific. The most common clinical manifestation is a palpable mass whereas in mammography the tumor most commonly appears as a round or oval mass without spiculated margins. Herein, a very rare case of NEBC is described in an asymptomatic patient who presented with an area of architectural distortion and the presence of microcalcifications that was incidentally detected on a screening mammography. A review of the literature has also been conducted. The diagnosis of NEBC requires a thorough investigation to exclude the possibility of a metastatic neuroendocrine tumor from another site because the two entities require different treatment approaches. Due to the rarity of the disease, the optimal therapeutic approach has not been clearly defined. Surgical resection is the mainstay of treatment. Further research is needed to better understand the molecular characteristics of NEBC and identify novel targeted therapies.

The rare entity of bilateral and unilateral neuroendocrine metastases to the breast: a case series and literature review

Introduction

Primary neuroendocrine neoplasms (NENs) in the breast are very rare. Until 2011, the prevalence was 0.1% of all breast lesions and 1% of all NENs, whereas metastatic breast NENs represent 1%–2% of all breast tumours. However, it seems that over the last 5 years the diagnostic frequency of breast NENs has increased, probably for more alert specialists and advanced diagnostic tools, leading to a prevalence of 2%–5% of diagnosed breast cancers, mostly in the elderly population. Breast metastases from extramammary malignancies are uncommon and bilateral ones are even more uncommon, with few reported in the literature. We describe four clinical settings of breast metastases from different NENs and the multidisciplinary approach for diagnosis and treatment.

Methods

Four patients were found to have NEN primaries metastasised to the breast. A literature review was conducted to identify similar cases and characterise breast metastases from neuroendocrinal tumors (NETs).

Results

Two patients presented with bilateral breast metastases (one with well-differentiated panNET and another with atypical lung carcinoid) and two had unilateral (one with moderately differentiated lung NET and one with atypical lung carcinoid). There are about 13 cases of NEN breast metastases reported in the English literature. The ileum is the most common primary site, followed by the appendix, duodenum, pancreas and lung.

Conclusion

Breast lesions from extramammary primary often pose a diagnostic challenge, since a breast nodule can be the first and often the only presentation of the disease. However, differentiating between primary and secondary NEN breast lesions is essential, owing to different clinical management and prognosis.

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.

Histopathological and Clinical Differences Between Primary Breast Carcinomas With Neuroendocrine Features and Primary Breast Carcinomas Mimicking Neuroendocrine Features

We aimed to determine the histopathological differences between primary breast carcinomas with neuroendocrine features (NEBC) and carcinomas mimicking neuroendocrine features (NEBC-like). Twenty-three cases with NEBC, all showing positive staining for synaptophysin and/or chromogranin-A in ≥50% of tumor cells and 36 cases with NEBC-like (no staining for neuroendocrine [NE] markers but suspicious for NE morphology in terms of solid/trabecular growth patterns) were included in the study. Significant differences were found between the groups in terms of the patients' ages, histologic/nuclear grade of tumor, lymphovascular invasion, comedo-type ductal carcinoma in situ (DCIS), microcalcification, Ki-67 proliferation index, nuclear shape, and level of peritumoral lymphocytic infiltration. The presence of large-size solid cohesive groups of tumor cells; plasmocytoid, spindle, and/or columnar shapes of tumor cells; and eosinophilic-granular appearance of cytoplasm were mostly noted in the NEBC group. The presence of small- to medium-sized solid cohesive groups of tumor cells; high-grade histologic and nuclear features; clear cytoplasm; and round to ovoid nucleus were mostly noted in the NEBC-like group. No significant differences were found in terms of tumor size, ER/PR/HER2 status, as well as the presence of DCIS, elastosis, extracellular/intracellular mucin, signet ring cells, apocrine features, and accompanying papilloma or ductal ectasia. In conclusion, small- to medium-sized solid cohesive groups of tumor cells, high-grade features, clear cytoplasm, round to ovoid shape of nucleus, lymphovascular invasion, comedo-type DCIS, microcalcification, high level of Ki-67 proliferation index (≥20%), and moderate/strong level of peritumoral lymphocytic infiltration might support non-NE features in breast carcinomas.

Metastases to the breast, an uncommon diagnosis: what do radiologists need to know?

OBJECTIVE

To analyze the imaging characteristics of histologically diagnosed metastases to the breast.

MATERIAL AND METHODS

We selected patients histologically diagnosed with metastases to the breast in our diagnostic and interventional breast imaging unit between March 2010 and September 2018.

RESULTS

A total of 9 patients (all women; mean age, 60 y; age range, 28-89 y) were diagnosed with metastases to the breast. In 1 (11.11%) case, the primary disease was diagnosed from the breast lesion. The primary tumors were melanoma (n=5), neuroendocrine tumor (n=2, one from the small bowel and one from the cervix), lung adenocarcinoma (n=1), and ovarian cancer (n=1). The clinical and imaging manifestations depend on the type of dissemination of disease and can simulate benign and malignant primary breast lesions.

CONCLUSION

There is no specific imaging pattern for metastases to the breast that would help to orient the diagnosis. It is important to consider this etiological possibility if the patient has a history of a primary tumor in another organ.

Expression of Insulinoma-Associated Protein 1 (INSM1) and Orthopedia Homeobox (OTP) in Tumors with Neuroendocrine Differentiation at Rare Sites

Insulinoma-associated protein 1 (INSM1) and orthopedia homeobox (OTP) are transcription factors that play a critical role in neuroendocrine (NE) and neuroepithelial cell development. INSM1 has been identified in multiple tumors of NE or neuroepithelial origin, whereas OTP expression has been mainly studied in NE tumors of pulmonary origin. Expression of OTP appears to correlate with poorer prognosis in pulmonary carcinoids; however, its expression patterns in other NE/neuroepithelial tumors need further investigation. Here, we assessed the diagnostic utility of INSM1 and OTP in tumors with NE differentiation at relatively uncommon sites including prostate, breast, and tumors of gynecologic origin. Thirty-two formalin-fixed, paraffin-embedded cases were used to construct a tissue microarray. Immunohistochemistry for INSM1 and OTP was performed and scored semi-quantitatively. INSM1 was diffusely expressed in 60% of gynecologic tumors, 71.4% of mammary carcinoma, and 25% of prostate adenocarcinoma with NE differentiation. Diffuse expression of OTP was detected in 50% of prostate adenocarcinoma with NE differentiation and 100% neuroendocrine carcinoma of the ovary. Immunostain for achaete-scute homolog 1, chromogranin, synaptophysin, and CD56 supported the NE and/or neuroepithelial differentiation of the tumors. In summary, INSM1 is expressed in most of the tumors with NE and neuroepithelial differentiation in this study, confirming the diagnostic utility of INSM1 as a novel and sensitive marker of NE/neuroepithelial differentiation. The expression of OTP in some NE tumors outside of lung expands the spectrum of tumors that may express this biomarker and should be considered when working up a NE tumor of unknown primary site.

Primary breast carcinomas with neuroendocrine features: Clinicopathological features and analysis of tumor growth patterns in 36 cases

Primary breast carcinoma with neuroendocrine features (NEBC) is an uncommon tumor. In the classification of WHO 2012, these tumors were categorized as: 1- neuroendocrine tumor, well-differentiated; 2- neuroendocrine carcinoma, poorly differentiated/small cell carcinoma; and 3- invasive breast carcinoma with neuroendocrine differentiation. In this study, we reviewed NEBC except poorly differentiated/small cell carcinoma variant in order to define the morphological growth patterns and cytonuclear details of these tumors. All breast surgical excision materials between 2007 and 2016 were re-evaluated in terms of neuroendocrine differentiation. Thirty-six cases showing positive staining for synaptophysin and/or chromogranin A in ≥50% of tumor cells were included in the study. All cases were female with a mean age of 67.4. Mean tumor diameter was 26 mm. Multifocality was noted in 5 cases. Grossly, they were mostly infiltrative mass lesions. T stages, identified in 34 cases, were as follows: 13 cases with pT1; 19 pT2 and 2 pT3. We described schematically 4 types of patterns depending on predominant growth pattern, except one case: 1) Large-sized solid cohesive groups (6 cases), 2) Small- to medium-sized solid cohesive groups with trabeculae/ribbons and glandular structures (6 cases), 3) Mixed growth patterns (20 cases), 4) Invasive tumor with prominent extracellular and/or intracellular mucin (3 cases). The tumor cells were mostly polygonal-oval with eosinophilic/eosinophilic-granular cytoplasm. The nuclei of tumor cells were mostly round to oval with evenly distributed chromatin. Only 5 cases showed high grade nuclear and histological features. Molecular subtypes of the cases were as follows: 33 luminal A, 2 luminal B, and 1 triple negative. NEBC should come to mind when a tumor display one of the morphological patterns described above, composed of monotonous cells with mild to moderate nuclear pleomorphism and abundant eosinophilic/eosinophilic granular or clear cytoplasm, especially in elderly patients.

Neuroendocrine Tumors of the Breast

Primary neuroendocrine tumors of the breast are a rare and underrecognized subtype of mammary carcinoma. Neuroendocrine tumors of the breast occur predominately in postmenopausal women. The tumors are subclassified into well-differentiated and poorly differentiated neuroendocrine tumors, and invasive breast carcinoma with neuroendocrine features. Well-differentiated tumors show architectural similarity to carcinoids of other sites but lack characteristic neuroendocrine nuclei. Poorly differentiated neuroendocrine tumors are morphologically identical to small cell carcinoma of the lung. Neuroendocrine differentiation, seen in up to 30% of invasive breast carcinomas, is most commonly associated with mucinous and solid papillary carcinomas. The diagnosis of neuroendocrine differentiation requires expression of the neuroendocrine markers synaptophysin or chromogranin. The main differential diagnosis is a metastatic neuroendocrine tumor from an extramammary site. Neuroendocrine tumors of the breast are treated similarly to other invasive breast carcinomas. Although no consensus has been reached on the prognosis, most studies suggest a poor outcome.

High-grade poorly differentiated neuroendocrine carcinoma of the breast with low oncotype Dx recurrence score: A case report

Primary neuroendocrine carcinoma of the breast (NECB) is a rare malignant tumor with controversial biological behavior and a lack of data guiding treatment decisions due to its scarcity. Cancer gene-expression profiling tests provide a better indication of clinical prognosis and help determine the best clinical management versus the traditional clinical and pathological parameters. This is a report of a NECB with a genetic assay that showed a low-risk tumor despite high-grade and poorly differentiated histopathological features. Patient outcomes correlate with the low risk classification without the need for adjuvant chemotherapy despite the standard clinical-pathologic approach. Analysis of cancer related genes expression and outcomes in historical NECB may elucidate new insight of this rare disease.

Primary neuroendocrine carcinoma of the breast: report of 2 cases and literature review

Neuroendocrine tumors of the breast are very rare accounting for less than 0.1% of all breast cancers and less than 1% of all neuroendocrine tumors. Focal neuroendocrine differentiation can be found in different histologic types of breast carcinoma including in situ and invasive ductal or invasive lobular. However, primary neuroendocrine carcinoma of the breast requires the expression of neuroendocrine markers in more than 50% of the cell population, the presence of ductal carcinoma in situ, and the absence of clinical evidence of concurrent primary neuroendocrine carcinoma of any other organ. Reports discussing the imaging characteristics of this rare carcinoma in different breast imaging modalities are scarce. We present 2 cases of primary neuroendocrine carcinoma of the breast for which mammography, ultrasound, and magnetic resonance imaging findings and pathology findings are described. A review of the medical literature on this particular topic was performed, and the results are presented.

Primary Neuroendocrine Carcinoma of the Breast: Histopathological Criteria, Prognostic Factors, and Review of the Literature

We present here a case of a 42-year-old woman diagnosed with primary neuroendocrine carcinoma of the breast (NECB). We discuss the importance of histological criteria for primary neuroendocrine mammary carcinoma, established by WHO in 2003 and 2012. After an overview of different cases of primary neuroendocrine carcinoma of the breast published in the literature, we present information about differential diagnosis, prognostic factors, and surgical and adjuvant treatment. Prognosis of NECB is not different from that of other invasive breast carcinomas and the most important prognostic factor is tumor grade (G). There is no standard treatment and patients should be treated similarly to patients with invasive ductal carcinoma, NOS (not otherwise specified), whose choice of therapy depends on tumor's size, degree of differentiation, clinical stage, and hormonal status.

Rare Malignant Tumors of the Breast

While the more common forms of breast cancer are well understood and recognized, there are many important rare malignancies that are less appreciated. Many of these cancers have imaging findings that, when understood, help to formulate a more educated differential diagnosis. In this article, the clinical features, imaging, and pathologic findings of rare breast malignancies will be discussed.

Spectrum of Extramammary Malignant Neoplasms in the Breast With Radiologic-Pathologic Correlation

Although primary breast cancer is the most common malignancy identified by breast imaging, extramammary malignancies may also rarely be encountered. These uncommon lesions may reflect primary neoplasms of nonmammary origin as well as secondary metastatic lesions, and include lymphoma, melanoma, neuroendocrine tumors, gastrointestinal tract malignancies, and angiosarcoma among other entities. Malignant extramammary breast lesions may be encountered during routine mammographic screening, identified during the diagnostic evaluation of a palpable breast abnormality, or may be detected incidentally during imaging of other organs of interest. As such, the radiologist should have familiarity with the appearance of these lesions. This article focuses on a review of several of the most common extramammary metastases to the breast, as well as a few lesions that may develop as either primary or secondary lesions.