Comparison of metastatic neuroendocrine neoplasms to the breast and primary invasive mammary carcinomas with neuroendocrine differentiation

Challenges in papillary tumors of breast

This review addresses common diagnostic challenges associated with papillary breast tumors-a rare but significant category of breast lesions. Despite their low incidence, papillary tumors are frequently encountered in breast pathology consultation practice due to their overlapping terminology and perplexing immunohistochemical results. Issues regarding assessment of invasive carcinoma in the setting of solid papillary carcinoma and encapsulated papillary carcinoma are covered. Emerging entities, such as tall cell carcinoma with reversed polarity and invasive lobular carcinoma mimicking solid papillary carcinoma, are discussed. Additionally, pragmatic guidance is provided for managing papillary breast tumors on needle core biopsy. Herein, we aim to provide clarity and confidence to surgical pathologists dealing with papillary breast tumors-mammary Medusa-equipping them with practical knowledge to better navigate this complex area of breast pathology.

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.

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.

Metastatic Neoplasms to the Breast

OBJECTIVE

When the clinical presentation is related to the metastatic mass and a radiologically solitary tumor focus is detected, especially in cases where clinical information is not taken into account or is insufficient, if a possible metastatic neoplasia is not kept in mind then it is possible to evaluate the tumor as a primary breast neoplasm. In this study, it is aimed to present our cases of non-hematopoietic metastatic neoplasms and to evaluate the clinicopathological features that may aid in distinguishing metastatic from primary neoplasms.

MATERIAL AND METHODS

This study includes cases diagnosed with metastatic non-hematopoietic breast neoplasm in breast resection materials in our center, between the years 2010-2023. All cases were analyzed retrospectively by evaluating clinicopathological features.

RESULTS

Of the 15 subjects included in the study, 11 (73%) were female and 4 (27%) were male. The mean age of the patients were 46.9 ranged from 22 to 63 years. The most frequent metastatic malignancy was carcinoma (60%), followed by melanoma (33%) and sarcoma (7%). Of the 9 patients with metastatic carcinoma, the primary tumor originated from the lungs in 4, from gastrointestinal system in 2, female genital tract in 2, and kidney in 1 patient. Sarcoma diagnosis was given in a single patient and the histology was a leiomyosarcoma originating from kidney.

CONCLUSION

A careful histomorphological and immunohistochemical evaluation and a detailed examination of the clinicoradiological data are critical to establish the right course in patient management, treatment plan and to correctly predict the prognosis.

Histopathological Features Predicting Neuroendocrine Morphology in Primary Breast Tumors: A Retrospective Analysis

Objective

Neuroendocrine neoplasms of primary breast tumors are rare compared to locations, such as the respiratory system and gastrointestinal system, where they are frequently observed. The diagnostic criteria for primary neuroendocrine tumors of the breast have been changed since first description. Morphological and immunohistochemical features helpful in their diagnosis, which vary due to the heterogeneous nature of these tumors, are highlighted in this retrospective study. The purpose was to determine specific histopathological features that can identify neuroendocrine morphology in primary breast tumors.

Materials and Methods

Cases diagnosed with invasive breast carcinoma from resection materials in a single center between 2011 and 2022 and in which neuroendocrine markers were investigated were included. Demographic information, initial histopathological diagnosis, presence of tumor in another organ, tumor location, size and surgical details of the cases were obtained from the hospital database and pathology reports. The slides were re-evaluated in terms of tumor growth pattern, cribriformity, tubule formation, nuclear features, prominence of nucleoli, palisading and basal location of nuclei, presence of grooves, cytoplasmic features and evidence of cytoplasmic border.

Results

The presence of basally located nuclei, absence of tubule formation, inconspicuous nucleoli, fine nuclear chromatin, granular cytoplasm and inconspicuous cytoplasmic borders were frequent findings in tumors with neuroendocrine features (p<0.05). These features may help differentiate primary breast tumors with neuroendocrine features from other breast carcinomas.

Conclusion

The histopathological features that are different from the specific features seen in classical neuroendocrine tumors, the absence of specific clinical and radiological findings, the inability to study neuroendocrine markers in every laboratory and the need to prove that the breast tumor is not a metastasis all create diagnostic difficulties for primary breast neuroendocrine neoplasms. We believe that the results of this study may help diagnose and identify more specific histomorphological features that help determine neuroendocrine morphology in primary breast tumors.

Breast Metastasis Arising from Ileal Neuroendocrine Tumor: an Unusual Presentation

Neuroendocrine tumors (NETs) up to 80% may have metastatic disease to lymph nodes, liver, and bones upon diagnosis due to their indolent course and benign nature. However, metastasis to the breast from gastropancreatic-neuroendocrine tumors (GEP-NETs) is unusual and rarely reported. Furthermore, such metastases may mimic a primary breast carcinoma clinically and radiologically. This case report illustrates an unusual presentation of metastasis to the right breast in addition to liver, pancreas, and lymph nodal metastases in a patient with ileal NET who was operated upon 5 years back. The metastases were detected by somatostatin receptor-based imaging and post-therapy scan which was confirmed by cytology and immunocytochemistry.

Neuroendocrine Tumor Metastases to the Breast: A Case Report and Review of the Literature

Breast metastases from neuroendocrine neoplasms (NENs) are considered infrequent. We report a case of a patient with ileocecal neuroendocrine tumor (NET) metastases to both breasts, for whom the initial clinical presentation was chronic diarrhea. Breast metastasis was initially suspected by a 68-Gallium DOTANOC positron emission tomography (PET)/CT and was confirmed by histopathology. We also performed a literature review in which we identified 116 cases of NENs metastatic to the breast reported so far. Most cases occurred in older women, were caused by NETs, and had the gastrointestinal tract as the primary site.

Clinicopathological Characteristics and Prognostic Profiles of Breast Carcinoma with Neuroendocrine Features

BACKGROUND

Breast carcinoma with neuroendocrine features includes neuroendocrine neoplasm of the breast and invasive breast cancer with neuroendocrine differentiation. This study aimed to investigate the clinicopathological features and prognosis of this disease according to the fifth edition of the World Health Organization classification of breast tumors.

MATERIALS AND METHODS

A total of 87 patients with breast carcinoma with neuroendocrine features treated in the First Medical Center, Chinese PLA General Hospital from January 2001 to January 2022 were retrospectively enrolled in this study.

RESULTS

More than half of the patients were postmenopausal patients, especially those with neuroendocrine neoplasm (62.96%). There were more patients with human epidermal growth factor receptor 2 negative and hormone receptor positive tumors, and most of them were Luminal B type (71.26%). The multivariate analysis showed that diabetes and stage IV disease were related to the progression-free survival of breast carcinoma with neuroendocrine features patients (p = 0.004 and p < 0.001, respectively).

CONCLUSION

Breast carcinoma with neuroendocrine features tended to be human epidermal growth factor receptor 2 negative and hormone receptor positive tumors, most of them were Luminal B type, and the related factors of progression-free survival were diabetes and stage IV disease.

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.

Small-cell breast carcinoma with response to atezolizumab: a case report

Background: Small-cell carcinoma of the breast is a rare disease with little research outlining molecular targets or optimal therapeutic management. We summarize a young female patient with poorly differentiated high-grade carcinoma with neuroendocrine features/small-cell carcinoma. Case presentation: A 31-year-old female presented with a large left breast mass. Initial biopsy revealed small-cell, triple-negative breast carcinoma. Treatment consisted of cisplatin and etoposide but was poorly tolerated and discontinued after one cycle. Combination abraxane/atezolizumab resulted in transient partial response in tumor size with 7 months of progression-free stability. Worsening metastatic disease was found 8 months after initial biopsy on radiologic studies and the patient expired 10 months after initial biopsy. Conclusion: Transient benefit in response to combination abraxane/atezolizumab was demonstrated.

Metastatic non-Hematopoietic Neoplasms to the Breast: A Study of 238 Cases

AIMS

The aim of this study was to review the clinicopathologic characteristics of metastatic non-hematopoietic malignancies to the breast, in order to identify salient features for practicing pathologist that are useful in distinguishing metastatic lesions from primary breast neoplasms.

METHODS AND RESULTS

A total of 238 cases were identified during the period from January 2005 to January 2015. Clinicopathologic features of these cases were retrospectively reviewed. Primary tumors included melanoma (99, 42%), serous carcinoma (35, 15%), neuroendocrine neoplasm (32, 13%), sarcoma (23, 10%), and adenocarcinoma from various organs (47, 20%), among others. Most metastases were unilateral (223, 94%) and unifocal (206, 87%), and were detected radiographically (167, 70%). Concurrent ipsilateral axillary metastasis occurred in 33 (14%) patients. Among 238 cases, 41 had metastatic disease to the breast concurrently or preceding the primary cancer diagnosis. Notable, in 39 (16%) cases, breast metastasis was the first clinical presentation of disease, and 16 (41%) of these cases were initially misdiagnosed as breast primaries. In contrast, with known history of non-mammary primary tumors, only 4 of 197 (2%) cases were misdiagnosed (p<0.0001).

CONCLUSIONS

Metastatic tumors share many overlapping features with breast primary carcinomas. However, cases with a well-circumscribed tumor, lack of in situ component, ER/PR negativity, and unusual morphologic features should raise the consideration of metastatic disease. While clinical history is paramount for correct diagnosis, metastasis to the breast as the first clinical presentation is not uncommon.

Overview of the 2022 WHO Classification of Neuroendocrine Neoplasms

In this review, we detail the changes and the relevant features that are applied to neuroendocrine neoplasms (NENs) in the 2022 WHO Classification of Endocrine and Neuroendocrine Tumors. Using a question-and-answer approach, we discuss the consolidation of the nomenclature that distinguishes neuronal paragangliomas from epithelial neoplasms, which are divided into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs). The criteria for these distinctions based on differentiation are outlined. NETs are generally (but not always) graded as G1, G2, and G3 based on proliferation, whereas NECs are by definition high grade; the importance of Ki67 as a tool for classification and grading is emphasized. The clinical relevance of proper classification is explained, and the importance of hormonal function is examined, including eutopic and ectopic hormone production. The tools available to pathologists for accurate classification include the conventional biomarkers of neuroendocrine lineage and differentiation, INSM1, synaptophysin, chromogranins, and somatostatin receptors (SSTRs), but also include transcription factors that can identify the site of origin of a metastatic lesion of unknown primary site, as well as hormones, enzymes, and keratins that play a role in functional and structural correlation. The recognition of highly proliferative, well-differentiated NETs has resulted in the need for biomarkers that can distinguish these G3 NETs from NECs, including stains to determine expression of SSTRs and those that can indicate the unique molecular pathogenetic alterations that underlie the distinction, for example, global loss of RB and aberrant p53 in pancreatic NECs compared with loss of ATRX, DAXX, and menin in pancreatic NETs. Other differential diagnoses are discussed with recommendations for biomarkers that can assist in correct classification, including the distinctions between epithelial and non-epithelial NENs that have allowed reclassification of epithelial NETs in the spine, in the duodenum, and in the middle ear; the first two may be composite tumors with neuronal and glial elements, and as this feature is integral to the duodenal lesion, it is now classified as composite gangliocytoma/neuroma and neuroendocrine tumor (CoGNET). The many other aspects of differential diagnosis are detailed with recommendations for biomarkers that can distinguish NENs from non-neuroendocrine lesions that can mimic their morphology. The concepts of mixed neuroendocrine and non-neuroendocrine (MiNEN) and amphicrine tumors are clarified with information about how to approach such lesions in routine practice. Theranostic biomarkers that assist patient management are reviewed. Given the significant proportion of NENs that are associated with germline mutations that predispose to this disease, we explain the role of the pathologist in identifying precursor lesions and applying molecular immunohistochemistry to guide genetic testing.

Epidemiology, Treatment and Prognosis Analysis of Small Cell Breast Carcinoma: A Population-Based Study

BACKGROUND

Primary small cell breast carcinoma (SCBC) is an uncommon malignancy with highly invasive behavior. The aim of this study was to find out more about the incidence, clinicopathologic characteristics and identify potential prognostic factors of SCBC.

METHODS

Data of patients with primary diagnosis of SCBC between 1975 and 2018 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. The incidence after adjustment for age and percentage change per year in incidence were calculated. Disease-specific survival (DSS) and overall survival (OS) were analyzed among these SCBC patients identified from the SEER database. The whole cohorts were randomized into training and validation cohorts as ratio of 7: 3. Cox regression analysis was performed to determine predictors of survival with the training cohorts. Predictive models were constructed with training cohorts, and nomogram validation was performed using receiver operating characteristic curves, concordance indices and calibration curves in both training and validation cohorts.

RESULTS

323 SCBC patients were enrolled finally during the research period. The overall incidence after adjustment for age between 1990 and 2018 was 0.14 per million per year, and the prevalence of the incidence has plateaued. Most of these tumors were poorly differentiated or undifferentiated. The most prevalent presenting stage was Stage II. Patients identified in this study were randomly divided into training (n = 226) and testing (n = 97) cohorts. Multivariate Cox proportional hazards model showed that chemotherapy, surgery and stage were important predictors of DSS and OS.

CONCLUSION

SCBC is considered an infrequent breast neoplasm with aggressive characteristics. Tumor stage is associated with poor prognosis. Combination of surgery and chemotherapy is the main treatment for SCBC.

Bilateral breast metastases as the first manifestation of an occult pancreatic neuroendocrine tumor

Breast metastases are uncommon findings compared to primary breast cancer and in particular bilateral secondary breast lesions from neuroendocrine tumor (NET)s are extremely rare with just less over 13 cases described in literature. We reported herewith the case of a 54-year-old woman who presented to our Breast Unit after noticing multiple, mobile, bilateral breast lumps. Imaging studies confirmed the presence of multiple, circumscribed, bilateral breast masses with slightly spiculated margins, classified as suspicious for malignancy (BI-RADS 4). A tru-cut biopsy was carried out on the largest lesion of each side and histopathologic and immunohistochemistry examination was consistent with metastases from pancreatic neuroendocrine tumor (PNET). Total-body CT revealed the presence of a mass located in the pancreatic body - tail with associated abdominal lymphadenopathies and multiple secondary nodules in bilateral breast and in the liver. Stage IV disease was diagnosed, patient did not undergo surgery and started LAR – octreotide therapy. Although rare, breast metastases from NETs represent an important diagnostic challenge for practitioners because of the difficulty to differentiate from a primary breast carcinoma or even from benign breast lesions. Clinicians should be aware of the possibility of bilateral breast metastases in differential diagnosis of breast lesions in order to ensure the correct diagnosis and the most appropriate management of these patients.

Lobular Breast Cancer: Histomorphology and Different Concepts of a Special Spectrum of Tumors

Simple Summary

Invasive lobular breast cancer (ILC) is a special type of breast cancer (BC) that was first described in 1941. The diagnosis of ILC is made by microscopy of tumor specimens, which reveals a distinct morphology. This review recapitulates the developments in the microscopic assessment of ILC from 1941 until today. We discuss different concepts of ILC, provide an overview on ILC variants, and highlight advances which have contributed to a better understanding of ILC as a special histologic spectrum of tumors.

Abstract

Invasive lobular breast cancer (ILC) is the most common special histological type of breast cancer (BC). This review recapitulates developments in the histomorphologic assessment of ILC from its beginnings with the seminal work of Foote and Stewart, which was published in 1941, until today. We discuss different concepts of ILC and their implications. These concepts include (i) BC arising from mammary lobules, (ii) BC growing in dissociated cells and single files, and (iii) BC defined as a morpho-molecular spectrum of tumors with distinct histological and molecular characteristics related to impaired cell adhesion. This review also provides a comprehensive overview of ILC variants, their histomorphology, and differential diagnosis. Furthermore, this review highlights recent advances which have contributed to a better understanding of the histomorphology of ILC, such as the role of the basal lamina component laminin, the molecular specificities of triple-negative ILC, and E-cadherin to P-cadherin expression switching as the molecular determinant of tubular elements in CDH1-deficient ILC. Last but not least, we provide a detailed account of the tumor microenvironment in ILC, including tumor infiltrating lymphocyte (TIL) levels, which are comparatively low in ILC compared to other BCs, but correlate with clinical outcome. The distinct histomorphology of ILC clearly reflects a special tumor biology. In the clinic, special treatment strategies have been established for triple-negative, HER2-positive, and ER-positive BC. Treatment specialization for patients diagnosed with ILC is just in its beginnings. Accordingly, ILC deserves greater attention as a special tumor entity in BC diagnostics, patient care, and cancer research.

Neuroendocrine carcinomas of the breast: Case series with review of literature

Background

The breast tumors with neuroendocrine differentiation show features similar to their counterparts in other organs. Neuroendorine carcinomas account for less than 0.1% of all breast carcinomas.

Aims

To study the demographics and clinicopathological prameters ten cases showing neuroendocrine carcinoma breast. Material and Methods: Ten cases showing neuroendocrine carcinoma were studied. The data was analysed for demographics and clinicopathological prameters. The Immunohistochemistry for ER, PR, Her2neu, Synaptophysin, Chromogranin, NSE, Ki67 index and EMA were done in these cases.

Results

Nine Trucut biopsies were reported as infiltrating duct carcinoma and one case as IDC with neuroendocrine differentiation with focal mucinous areas.The histopathological slides of breast excision specimens revealed clusters of cells arranged in sheets and small nests separated by thin fibrous septae in eight of the cases. Trabeculae were noted in two case and in another rosettes were noted. DCIS component was noted in two cases. Infiltration into fat in five of the cases. One case showed pools of mucin. The tumour cells were positive for synaptophysin in 5/10 cases, chromogranin in 8/10 cases and NSE in 9/10 cases. Estrogen receptor positivity was noted 6 cases (6/10), progesterone receptor positivity in 8 cases (8/10) and Her2neu positivity in 5 cases (5/10).

Conclusion

NECB cases are more likely to ER/PR positive with variability of expression of neuroendocrine markers. These tumors are more aggressive with propensity for distant metastasis. Endocrine therapy may be more beneficial than standard chemotherapy. Anti-angiogenic markers are an exciting new approach for these case, which is yet to be explored.

Breast cancer with neuroendocrine differentiation: an update based on the latest WHO classification

Breast cancers with neuroendocrine (NE) differentiation are very heterogeneous, comprising broadly cancers that are morphologically similar to NE tumors (NET) of other anatomic sites, infiltrating breast carcinomas, no special type (IBC-NST) and other special subtypes with NE morphology and/or NE markers expression. Depending on the classification schemes, they are variably included into "NE breast cancers". The latest WHO classification harmonized NE breast cancers with NE neoplasms (NEN) of other organ systems, defined NEN into well-differentiated NET (low Nottingham grade) and poorly-differentiated NE carcinoma (NEC) (high Nottingham grade). Other IBC with NE differentiation are diagnosed based on solely the non-NEN component. Due to the changes in diagnostic criteria, variable results were obtained in the previous studies on NE breast cancers. Hence, the clinical value of NE differentiation in breast cancers is not well investigated and understood. In this review, the current understanding in the pathogenesis, clinical, prognostic, immunhistochemical, and molecular features of "NE breast cancers" is summarized. Controversial issues in their diagnosis and classification are also discussed.

Neuroendocrine Carcinomas of the Canine Mammary Gland: Histopathological and Immunohistochemical Characteristics

Invasive mammary carcinomas with neuroendocrine differentiation are rare in women and were reported only once in female dogs. For the present study, ten cases of solid mammary carcinoma positive for chromogramin A in immunohistochemistry were selected. Histopathological characteristics of these tumors were described and immunohistochemical evaluation was performed with chromogranin A, synaptophysin, CD56, NSE, PGP 9.5, pancitokeratin, Ki67, estrogen receptor (ER), and progesterone receptor (PR). The average animal age was 13.2 years old and the average tumor size was 4.8 cm. In total, 70% of the neoplasms were classified as grade III and 30% as grade II by the Nottingham histological grade system. High mitotic index was observed with a mean of 27.5 mitoses in 10 high magnification fields. Only one case showed typical carcinoid tumor characteristics. In addition, vascular invasion was shown in 3 tumors. All carcinomas were positive for chromogran A, while only two cases were reactive to synaptophysin. For PGP 9.2, NSE and CD56, we observed positivity of 100, 90, and 70%, respectively, in the samples, being that no tumor was positive for all the neuroendocrine markers. All neoplasms showed ER and PR in at least 10% of neoplastic cells, while Ki67 varied from 29 to 95%, with mean mitotic index of 67%. Four of the ten animals died within 1 year of the tumor diagnosis. Neuroendocrine neoplasms occur in the canine mammary gland and are propably underdiagnosed. This is due to their non-specific morphological characteristics and the low use of neuroendocrine immunohistochemistric markers the diagnostic routine. More studies are necessary to determine the prognosis of this new histological type.

On the Endless Dilemma of Neuroendocrine Neoplasms of the Breast: a Journey Through Concepts and Entities

Neuroendocrine differentiation in breast carcinomas has been a matter of discussion since it was first described almost 60 years ago. Indeed, so-called neuroendocrine neoplasms of the breast (Br-NENs) are a less well-defined group of neoplasms than analogous entities in other anatomic sites, such as the lung and the gastroenteropancreatic (GEP) tract. Pure neuroendocrine phenotype is extremely rare, whereas the expression of neuroendocrine markers in usual breast carcinomas, both of special and of non-special type, without evident neuroendocrine morphology, is more common. In this context, the diagnostic criteria and the classification scheme for Br-NENs have been continuously changing over time and real consensus on this topic is still lacking, despite the recent publication of the 5th edition of the WHO classification of breast tumors. In this review, we will recapitulate the evolution of the concept of Br-NEN; revise the available knowledge on their morphological, molecular, and clinical features; and critically discuss the current classification scheme.

Investigation of somatostatin receptor profile of neuroendocrine carcinomas of the breast

Carcinomas of the breast with neuroendocrine features are rare primary neoplasms positive for neuroendocrine markers. According to the WHO classification of tumours of the breast they are divided into three morphologically distinct categories. They comprise neuroendocrine tumour (NET), neuroendocrine carcinoma (NEC) and carcinoma with neuroendocrine differentiation (NED). The purpose of this study was to investigate for the first time the full spectrum of sstr expression status in breast carcinomas with neuroendocrine features. Fifteen primary breast carcinomas with histological and immunohistochemical neuroendocrine features were studied. Four of them were classified as NETs and two as NECs, and the remaining 9 as carcinomas with NED. All six types of somatostatin receptor (sstr) types (sstr1, sstr 2A, sstr2B, sstr3, sstr4 and sstr5) were investigated by immunohistochemistry. To assess the distribution and intensity of membranous receptor immunoreactivity, a four-scale scoring system was used. Overall predominant receptors were sstr2A, sstr2B, sstr3 and sstr5 showing the highest membranous staining scores 3+ and 2 + . The sstr1 was not detected. Given that carcinomas with neuroendocrine features represent distinct entities, patients with such tumours may benefit from sstr targeting therapies. Immunohistochemistry for sstrs can predict the effectiveness of administration of SST analogues to those patients, thus contributing to achieve the maximum therapeutic outcome, particularly in NETs and NECs with scores 2+ and 3 + .

Histological clues to the diagnosis of metastasis to the breast from extramammary malignancies

AIMS

The aims of this study were to review the histological features useful for the identification of metastases to the breast and to investigate the impression that this diagnosis has become more common.

METHODS AND RESULTS

The histological features of metastases to the breast from 2008 to 2018 were reviewed. Seventy-four biopsies from 66 patients were identified: 1% compared with primary carcinoma of the breast. Non-haematological metastases comprised 0.75% compared with 0.3% in a series from 1996 to 2005. The most common tumour types were pulmonary carcinoma (22), lymphoma (15), melanoma (13), gastrointestinal carcinoma (eight) and serous papillary carcinoma (four). In 73% there were histological features that were not typical of primary mammary carcinoma. Some metastases were histologically similar to breast cancer and the history was essential to making the correct diagnosis. Useful histological clues included small-cell morphology for pulmonary carcinoma, glands containing necrosis for gastrointestinal carcinoma, intranuclear inclusions, marked pleomorphism and spindle cells for melanoma, clear cells for renal carcinoma, papillary architecture for serous papillary carcinoma and sheets of centroblasts or nodules of centroblasts and centrocytes for lymphoma. Useful immunohistochemical markers included TTF-1 for pulmonary carcinoma, S100, melan-A and HMB45 for melanoma, CK20 and CDX2 for colorectal carcinoma, PAX8 and WT1 for serous papillary carcinoma and lymphoid markers for lymphomas, in addition to the absence of expression of mammary markers ER, GATA3 and GCDFP-15.

CONCLUSION

The majority of metastases to the breast have histological clues to the diagnosis. Immunohistochemistry is helpful. This diagnosis is being made more frequently.

Medullary Thyroid Carcinoma Presenting as Metastatic Disease to the Breast

Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor that is derived from C cells of the thyroid gland. It is a rare aggressive tumor, known to metastasize to lymph nodes, liver, bones, and lungs. A 41-year-old female, who presented with a breast mass, was initially diagnosed with invasive ductal carcinoma. She was also found to have a thyroid mass which was later diagnosed as MTC. On a rereview of the breast pathology, the morphologic features were strikingly similar to the MTC. Further investigation revealed that this was in fact a very rare case of MTC that had metastasized to the breast. We have identified 20 cases of MTC metastasizing to the breast in the literature that supports its occurrence as a real possibility. Albeit rare, medullary thyroid carcinoma should be considered in the differential diagnosis of a breast mass.

Previously undiagnosed neuroendocrine tumour mimicking breast cancer metastasis to the orbit

Metastatic neuroendocrine neoplasms to the breast are rare and histopathologic overlap with mammary carcinomas has led to misdiagnosis. We present a case of a middle-aged woman with diplopia and a right medial rectus mass. Metastatic breast cancer was initially suspected based on a history of invasive ductal carcinoma. Detailed immunohistochemistry of the orbital biopsy, gallium-68 dotatate positron emission tomography-CT, and reevaluation of her prior breast specimen, demonstrated that her initial breast carcinoma diagnosis was in error and she was ultimately diagnosed with a previously unknown gastrointestinal neuroendocrine tumour metastatic to both the orbit and breast. This case highlights the challenges of differentiating between metastatic neuroendocrine tumours and invasive mammary carcinomas with neuroendocrine differentiation both in the breast and in the orbit. It is important to recognise the overlap so that a primary neuroendocrine neoplasm is not missed, or treatment significantly delayed.

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.

Neuroendocrine neoplasms of the breast: A review focused on the updated World Health Organization (WHO) 5th Edition morphologic classification

Neuroendocrine breast neoplasms are uncommon invasive carcinomas that have historically been poorly defined due to various definitions of what constitutes a neuroendocrine carcinoma. The 5th Edition of the World Health Organization (WHO) Classification of Breast Tumors has moved to a dichotomous classification of neuroendocrine neoplasms in the breast in order to become standardized with classifications of other organ systems. Neuroendocrine breast neoplasms in the new edition are classified as "neuroendocrine tumor" and "neuroendocrine carcinoma." Key changes are exclusion of special histologic types (solid papillary carcinoma and hypercellular variant of mucinous carcinoma) and the inclusion of large cell neuroendocrine carcinoma. Neuroendocrine tumors are genetically heterogenous and harbor molecular alterations that differ from invasive carcinoma, no special type. Neuroendocrine carcinomas (high-grade) show some overlapping molecular alterations with their counterparts in other organ systems. Data regarding the prognostic significance of neuroendocrine differentiation are conflicting, and histologic grade and tumor stage remain the main prognostic parameters. Current management of neuroendocrine neoplasms is not different from other types of breast carcinoma. This review will provide an update to the current WHO classification of neuroendocrine breast neoplasms and describe pertinent clinical, histologic, and molecular features of these uncommon tumors.

Primary Neuroendocrine Neoplasms of the Breast: Case Series and Literature Review

Primary neuroendocrine carcinoma of the breast (NECB) as defined by the World Health Organization (WHO) in 2012 is a rare, but possibly under-diagnosed entity. It is heterogeneous as it entails a wide spectrum of diseases comprising both well-differentiated neuroendocrine tumors of the breast as well as highly aggressive small cell carcinomas. Retrospective screening of hospital charts of 612 patients (2008–2019) from our specialized outpatient unit for neuroendocrine neoplasia revealed five patients diagnosed with NECB. Given the low prevalence of these malignancies, correct diagnosis remains a challenge that requires an interdisciplinary approach. Specifically, NECB may be misclassified as carcinoma of the breast with neuroendocrine differentiation, carcinomas of the breast of no special type/invasive ductal carcinoma, or a metastasis to the breast. Therefore, this study presents multifaceted characteristics as well as the clinical course of these patients and discusses the five cases from our institution in the context of available literature.

EPB41L5 is Associated With the Metastatic Potential of Low-grade Pancreatic Neuroendocrine Tumors

BACKGROUND/AIM

Low-grade pancreatic neuroendocrine tumors (LG-PNETs) behave unpredictably. The aim of the study was to identify biomarkers that predict PNET metastasis to improve treatment selection.

PATIENTS AND METHODS

Five patients with primary non-metastatic LG-PNETs, six with primary LG-PNETs with synchronous or metachronous metastases (M-PNETs), and six metastatic to liver LG-PNETs (ML-PNETs) from the group of six M-PNET patients were selected. RNA data were normalized using iterative rank-order normalization. Student's t-test identified differentially-expressed genes in LG-PNETs versus M-PNETs. A 2-fold difference in expression was considered to be significant. Results were validated with an independent dataset of LG-PNETs and metastatic LG-PNETs.

RESULTS

Overall, 195 genes had a >2-fold change (in either direction). A total of 29 genes were differentially overexpressed in M-PNETs. Erythrocyte membrane protein band 4.1-like 5 (EPB41L5) had a 2.07-fold change increase in M-PNETs and the smallest p-value. EPB41L5 was not statistically different between M-PNETs and ML-PNETs. EPB41L5 differential expression between primary and metastatic LG-PNETs was confirmed by immunohistochemistry.

CONCLUSION

These results support further investigation into whether EPB41L5 is a biomarker of PNETs with high risk for metastases.

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.

A case report on metastatic ileal neuroendocrine neoplasm to the breast masquerading as primary breast cancer: A diagnostic challenge and management dilemma

RATIONALE

Metastatic neuroendocrine neoplasms (NENs) to the breast are very rare entities comprising only 1% to 2% of all metastatic breast tumors. In this article, we describe a case of a neuroendocrine ileal neoplasm metastatic to breast and liver, with breast metastatic tumor to be the initial manifestation of the disease.

PATIENT CONCERNS

We herein report a rare case of a female patient admitted to our department with a palpable painful mass on her left breast.

DIAGNOSIS

The surgical and histological investigation revealed a metastatic neuroendocrine neoplasm to the breast originated from terminal ileum.

INTERVENTIONS

A left lumpectomy, right hemicolectomy, cholecystectomy, left hepatectomy along with liver metastasectomies (V, VI, VIII) plus radiofrequency ablation of lesions to the right liver lobe plus standard lymphadenectomy was performed.

OUTCOMES

Considering the advanced stage of the disease, the patient received an adjuvant therapy of somatostatin analog plus everolimus. Under the guidance of oncological consultation, patients follow-up with CT and MRI scan and clinical re-evaluations in the first 3 and 6 months, substantiates no evidence of recurrence and she presents herself asymptomatic.

LESSONS

An appropriate level of suspicion and selective immunohistochemistry in these cases, particularly where no prior history of a known primary neuroendocrine neoplasm occurs, may help to diagnose a previously undetected neuroendocrine tumor elsewhere in the body and provide guidance for the appropriate treatment selection.

Phosphatidylinositol 3-kinase pathway genomic alterations in 60,991 diverse solid tumors informs targeted therapy opportunities

Background

The phosphatidylinositol 3‐kinase (PI3K) pathway is frequently altered in cancer. This report describes the landscape of PI3K alterations in solid tumors as well as co‐alterations serving as potential resistance/attenuation mechanisms.

Methods

Consecutive samples were analyzed in a commercial Clinical Laboratory Improvement Amendment‐certified laboratory using comprehensive genomic profiling performed by next‐generation sequencing (315 genes). The co‐alterations evaluated included the Erb‐B2 receptor tyrosine kinase 2 (ERBB2), ERBB3, ERBB4, RAS, MET proto‐oncogene tyrosine kinase (MET), and mitogen‐activated protein kinase kinase (MAP2K) genes as well as tumor protein 53 (TP53), estrogen receptor 1 (ESR1), and androgen receptor (AR).

Results

Alterations in any of 18 PI3K‐pathway associated genes were identified in 44% of 60,991 tumors. Although single base and insertions/deletions (indels) were the most frequent alterations, copy number changes and rearrangements were identified in 11% and 0.9% of patients, respectively. Overall, the most frequently altered genes were PIK3 catalytic subunit α (PIK3CA) (13%), phosphatase and tensin homolog (PTEN) (9%), and serine/threonine kinase 11 (STK11) (5%). Tumor types that frequently harbored at least 1 PI3K alteration were uterine (77%), cervical (62%), anal (59%), and breast (58%) cancers. Alterations also were discerned frequently in tumors with carcinosarcoma (89%) and squamous cell carcinoma (62%) histologies. Tumors with a greater likelihood of co‐occurring PI3K pathway and MAPK pathway alterations included colorectal cancers (odds ratio [OR], 1.64; P < .001), mesotheliomas (OR, 2.67; P = .024), anal cancers (OR, 1.98; P = .03), and nonsquamous head and neck cancers (OR, 2.03; P = .019). The co‐occurrence of ESR1 and/or AR alterations with PI3K alterations was statistically significant in bladder, colorectal, uterine, prostate, and unknown primary cancers.

Conclusions

Comprehensive genomic profiling reveals altered PI3K‐related genes in 44% of solid malignancies, including rare disease and histology types. The frequency of alterations and the co‐occurrence of resistance pathways vary by tumor type, directly affecting opportunities for targeted therapy.

Comprehensive genomic profiling of solid tumors reveals frequent genetic alterations in several genes of the phosphatidylinositol 3‐kinase (PI3K) pathway. Data from this analysis suggest that in‐depth characterization of the PI3K pathway along with concomitant resistance alterations in other pathways can provide a genomic background for the development of future treatments.

[A misleading breast metastasis of medullary thyroid carcinoma]

Recognition of mammary metastases by pathologists is fundamental because their prognosis and treatment are different from those of primary mammary carcinomas. We report the case of a 54-year-old woman presenting on her mammography a left breast nodule known for 5 years, having discreetly increased in size. Breast ultrasound showed a regular 1.2cm hypoechogenic nodular formation. A microbiopsy was performed. On microscopic examination, we observed a tumor proliferation realizing nests within a small, richly vascularized stroma. The tumor cells had a moderately abundant, eosinophilic, granular cytoplasm and a rounded, slightly atypical nucleus. One mitosis was found for 10 fields at×400 magnification. Tumor cells did not express hormone receptors but chromogranin A, synaptophysin, TTF1 and thyrocalcitonin. The proliferation index established by the anti-Ki67 antibody was 5 %. The diagnosis was a secondary localization of a well-differentiated neuroendocrine tumor which immunohistochemical profile firstly suggests a thyroid origin. We later learned that the patient had a history of total thyroidectomy 13 years ago. It was a sporadic medullary carcinoma of the thyroid. Bone scintigraphy revealed a lacunar lesion of the posterior part of the right iliac wing suspicious of secondary location. This right iliac lesion was biopsied. It was also a localization of the medullary thyroid carcinoma. The final diagnosis is a metastatic medullary thyroid carcinoma, slowly progressive, the mammary metastasis having probably existed for 5 years.

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.

Merkel cell carcinoma, melanoma, metastatic mimics of breast cancer

Merkel cell carcinoma and melanoma can each occur primarily in breast skin, or metastasize to the breast. The breast is a rare site of metastasis of essentially any and every type of tumor, including carcinomas, sarcomas, and hematolymphoid neoplasms, and 10-30% of breast metastases may represent the initial presentation of disease. Although metastases generally recapitulate histologic features of the primary tumor, they are diagnostically challenging given their rarity and morphologic overlap with breast carcinoma, including special types of breast cancer. Histologic clues may include lack of carcinoma in situ, lack of central elastosis, pattern of infiltration around normal breast structures, yet none of these are specific. Careful correlation with clinical history and judicious use of immunostain panels is essential in approaching these cases.

Neuroendocrine Tumors of the Breast

A small but increasingly recognized and studied subset of breast carcinomas are characterized by neuroendocrine (NE) differentiation. As with nearly all forms of breast neoplasia, NE tumors are characterized by considerable heterogeneity in microscopic appearance and clinical aggressiveness. About half of NE breast carcinomas recapitulate the histological spectrum typical of their counterparts in other organ systems, varying from "carcinoid-like" to small cell carcinoma, with most representing intermediate grade tumors. Despite NE morphology, these tumors have a high frequency of estrogen receptor expression. Clinical outcomes of women with NE breast carcinomas are reliably grade and stage dependent. Tumors associated with "solid papillary" differentiation comprise the remaining cases of NE breast neoplasia. Solid papillary carcinoma is an intrinsically low grade/favorable prognosis class of breast neoplasia that usually presents in post-menopausal age groups. About half of solid papillary carcinoma present as a distinctive pattern of ductal carcinoma in situ that may be difficult to recognize owing to its close resemblance to florid proliferative lesions. Invasive solid papillary carcinomas are characterized by a variety of histological patterns and often show mucinous differentiation. Future studies are necessary to better define the histogenesis, optimal classification, and improved directed therapies for NE breast neoplasia.

Primary lung carcinoid metastatic to the breast

Lung carcinoid tumors account for approximately 2% of lung cancers, with 10% of the tumors represented by the atypical type. While atypical carcinoids are metastatic to intrathoracic lymph nodes in approximately half of the cases on the initial presentation, distant metastases are seen in only 20% of the patients and are found most frequently in bones, liver, adrenal glands, and brain. We present a case of an unusual metastatic disease to the breast in 51-year-old female who developed a new breast mass 2 years after left lower lobectomy due to atypical carcinoid tumor. Atypical pulmonary carcinoid metastases to the breast are exceptionally uncommon, yet they are important considerations for appropriate management, especially with an anamnesis of this neoplasm.

Cytomorphology of metastatic pituitary carcinoma to the bone

Metastatic pituitary carcinoma to bone is rare. In this report, we present a case of a 59-year-old female with recurrent pituitary adenoma of the sparsely granulated somatotroph subtype with metastasis to a few bony sites 10 years later. Needle core biopsy (NCB) with touch preparations was performed on a 5 mm lesion in left ilium. Diff-Quik stained NCB touch preparation slides showed a few loosely cohesive epithelial polygonal cells that were arranged in nests or acini, or singly, had scant vacuolated cytoplasm and eccentrically located round nuclei (plasmacytoid) with slight nuclear pleomorphism, fine granular chromatin, conspicuous nucleoli, and smooth nuclear membrane. Trilineage hematopoietic cells of bone marrow were also appreciated in the background. H&E stained core sections showed fragments of bone and bone marrow with nests of bland epithelial cells with similar cytomorphology as seen in NCB touch preparation slides. The tumor cells were immunoreactive for juxtanuclear dot-like staining of pan-cytokeratin (CAM 5.2 and AE1/AE3) (a specific feature), neuroendocrine markers (CD56, synaptophysin, and chromogranin. Additionally, scattered cells were immunoreactive for growth hormone. Molecular test showed that tumor cells were negative for the promoter methylation of O-6-Methylguanine-DNA Methyltransferase (MGMT). Final diagnosis of metastatic pituitary carcinoma was rendered. Morphology of metastatic pituitary carcinoma, its differential, clinical presentation and treatment were discussed. Diagn. Cytopathol. 2017;45:645-650. © 2017 Wiley Periodicals, Inc.

A case of multicentric low-grade neuroendocrine breast tumor with an unusual histological pattern

Neuroendocrine features are detectable in carcinomas of the breast either as scattered cells, that are recognized by their expression of neuroendocrine cell markers. Instead, pure breast carcinomas with neuroendocrine features (NEBC) are very rare and represent <1% of all breast cancer. Usually NEBC may be well or poorly differentiated and more frequent in older woman. These tumors showed variable histological pattern but a common feature is represented by expression of neuroendocrine markers. Here we report a case of a primary multicentric low-grade neuroendocrine carcinoma of the breast presented because of its rarity and for the unusual tubular and cribriform pattern resembling a well-differentiated conventional breast carcinoma. The tumor was treated with left quadrantectomy with concomitant wide excisional biopsy of other two nodules and lymph node sentinel biopsy. No recurrence was observed during 1-year follow-up. Because of its rarity and variability of morphologic features, there exist diagnostic challenges for pathologists to differentiate primary NEBC to some conventional breast carcinomas and to the breast metastasis from neuroendocrine tumor of the lung or gastrointestinal tract. It is important to be able recognize this tumor in order to avoid potential misdiagnosis and improper management of afflicted patients.