Invasive carcinoma with neuroendocrine differentiation of the breast showing triple negative, large and basal cell-like features

Management of Neuroendocrine Breast Carcinoma (NEBC): Review of Literature

Extra pulmonary high-grade poorly differentiated neuroendocrine carcinomas (EP-NECs) are rare tumors that usually arise in the gastrointestinal and genitourinary tracts. Primary neuroendocrine carcinoma of the breast (NEBC) is extremely rare, representing less than 0.1% of all breast cancers and less than 1% of neuroendocrine neoplasms. Consequently, they can be misdiagnosed as other types of breast cancer, however, proper immunohistochemical (IHC) studies can assist with making the correct diagnosis. Management of NEBC can be challenging given the paucity of evidence-based literature and should not routinely follow the therapeutic guidelines of other breast cancers. In this article, we review the current literature regarding the management of NEBC.

MYC Deregulation and PTEN Loss Model Tumor and Stromal Heterogeneity of Aggressive Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) patients have a poor prognosis and few treatment options. Mouse models of TNBC are important for development of new therapies, however, few mouse models represent the complexity of TNBC. Here, we develop a female TNBC murine model by mimicking two common TNBC mutations with high co-occurrence: amplification of the oncogene MYC and deletion of the tumor suppressor PTEN. This Myc;Ptenfl model develops heterogeneous triple-negative mammary tumors that display histological and molecular features commonly found in human TNBC. Our research involves deep molecular and spatial analyses on Myc;Ptenfl tumors including bulk and single-cell RNA-sequencing, and multiplex tissue-imaging. Through comparison with human TNBC, we demonstrate that this genetic mouse model develops mammary tumors with differential survival and therapeutic responses that closely resemble the inter- and intra-tumoral and microenvironmental heterogeneity of human TNBC, providing a pre-clinical tool for assessing the spectrum of patient TNBC biology and drug response.

Neuroendocrine tumor of the breast showing invasive micropapillary features and multiple lymph node metastases

BACKGROUND

Herein, for the first time, we present a case with mixed invasive micropapillary and neuroendocrine mammary neoplasm.

CASE

The patient, a 65-year-old postmenopausal woman, had become aware of a tumor in her right breast 11 months prior to presentation at our hospital. The cut surface of the mastectomy specimen contained a well-circumscribed, multinodular, red-brown tumor, measuring 15x15x15 cm. Histopathologically, this solid cystic lesion consisted of medullary growth of cancer cells accompanied by a well-developed vascular network as well as conspicuous hemorrhage. Cancer cell nests of various sizes displayed an "inside-out" structure surrounded by empty spaces. Most cancer cells were polygonal, though a few were short fusiform-shaped, and possessed finely granular, eosinophilic cytoplasm and ovoid, fine-granular nuclei. Eighteen mitotic figures were observed in 10 high-power fields. Macrometastases, up to 13x8 mm in size, with the same morphological features as the original tumor site, were identified in 3 of 15 dissected right axillary nodes. Immunohistochemically, primary and metastatic cancer cells were diffusely positive for chromogranin A and the estrogen receptor (Allred's total score: 8) and focally reactive for synaptophysin and the progesterone receptor (total score: 5). HER2 and cytokeratin 5/6 were negative, and the MIB-1 labelling index was 36.2%. MUC1 and EMA lined the stroma-facing surfaces of the cell membranes, indicating reversed polarity.

CONCLUSION

Our current patient, who had an invasive breast carcinoma with concomitant neuroendocrine and micropapillary features, developed multiple nodal metastases in association with a large-diameter tumor showing a luminal B-like immuno-profile. Accordingly, meticulous clinical follow-up remains essential for this uncommon case.

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 breast carcinoma: a rare but challenging entity

Breast carcinoma with neuroendocrine differentiation, also known as neuroendocrine breast carcinoma (NEBC), includes a heterogeneous group of rare tumors, which account for 2–5% of all invasive breast carcinomas. Because of their low incidence, most of the current limited knowledge of these tumors derives from anecdotal case reports or small retrospective series. The diagnosis of NEBC is based on the presence of morphological features similar to gastrointestinal and lung NETs and neuroendocrine markers. NEBCs are usually hormone receptors positive and HER2 negative, but despite this luminal phenotype, most recent studies suggested that NEBC could be associated with worse prognosis compared to invasive breast cancer without neuroendocrine differentiation. Due to its rarity and lack of randomized data, there is little evidence to guide the choice of treatment, so NEBC is currently treated as any invasive breast carcinoma not-otherwise specified. Recently, attempts to molecularly characterize NEBC have been made, in order to provide new targets for a more personalized treatment of this uncommon entity.