Neuroendocrine tumours of the breast: a genomic comparison with mucinous breast cancers and neuroendocrine tumours of other anatomic sites

The clinicopathological and molecular features of primary high-grade neuroendocrine tumour in the breast

AIMS

Nottingham grade for breast cancers, rather than gastro-entero-pancreatic (GEP) grade for neuroendocrine tumours (NETs), is currently applied to primary breast NETs, which need further clarification. High-grade NETs in breast also remain poorly recognised.

METHODS AND RESULTS

Among 595 breast carcinomas with diffuse synaptophysin (Syn) or chromogranin A (CgA) immunostaining (≥ 90%), 197 eligible cases were selected, including 69 NETs, 123 invasive breast carcinomas of no special type (IBC-NSTs) and five neuroendocrine carcinomas (NECs). The prognostic significance of these two grading systems in breast NETs was assessed. Furthermore, the clinicopathological features were compared in Nottingham G3 cases among three entities. Targeted sequencing and immunostaining (INSM1/p53/Rb/p16) were also performed in all Nottingham G3 NETs, NECs and 10 Nottingham G3 IBC-NSTs. All Nottingham G3 NETs (9 of 69, 13.0%) fell into GEP G3 cases (20 of 69, 29.0%). Nottingham grade provided better prognostic discrimination between G1/G2 and G3 NETs than GEP grade. Among Nottingham G3 cases, there was a trend towards reduced progression-free survival (PFS) in NETs compared with IBC-NSTs (P = 0.057), and the former were more often immunoreactive for INSM1 (44.4 versus 0%, P = 0.033). Nottingham G3 NETs were all of luminal-like phenotype (P < 0.001) and exhibited less aberrant p53 patterns (11.1 versus 80.0%, P = 0.023) as well as more favourable PFS (P = 0.012) and disease-specific survival (P = 0.002) than NECs. Rb loss (4 of 5, 80%), p16 overexpression (5 of 5, 100%) and RB1 mutation (2 of 5, 40%) were observed exclusively in NECs. Based on expression data, epithelial-mesenchymal transition and KRAS signalling pathways were significantly up-regulated in Nottingham G3 NETs (P < 0.05).

CONCLUSIONS

Nottingham grade, rather than GEP grade, holds important prognostic significance in primary breast NETs. Nottingham G3 NETs represent a small proportion of breast NETs, and may demonstrate distinct clinicopathological and molecular features from other high-grade breast carcinomas with diffuse neuroendocrine markers expression.

Additional report: recurrence of intraductal papilloma with atypical ductal hyperplasia as solid papillary carcinoma

We report a case of solid papillary carcinoma (SPC) that developed at the site of a previous intraductal papilloma (IDP) with atypical ductal hyperplasia. This case supports IDP as a potential precursor lesion to SPC.

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.

Unraveling complexity and leveraging opportunities in uncommon breast cancer subtypes

Special histologic subtypes of breast cancer (BC) exhibit unique phenotypes and molecular profiles with diagnostic and therapeutic implications, often differing in behavior and clinical trajectory from common BC forms. Novel methodologies, such as artificial intelligence may improve classification. Genetic predisposition plays roles in a subset of cases. Uncommon BC presentations like male, inflammatory and pregnancy-related BC pose challenges. Emerging therapeutic strategies targeting genetic alterations or immune microenvironment are being explored.

Molecular Basis of Breast Tumor Heterogeneity

Breast cancer (BC) is a profoundly heterogenous disease, with diverse molecular, histological, and clinical variations. The intricate molecular landscape of BC is evident even at early stages, illustrated by the complexity of the evolution from precursor lesions to invasive carcinoma. The key for therapeutic decision-making is the dynamic assessment of BC receptor status and clinical subtyping. Hereditary BC adds an additional layer of complexity to the disease, given that different cancer susceptibility genes contribute to distinct phenotypes and genomic features. Furthermore, the various BC subtypes display distinct metabolic demands and immune microenvironments. Finally, genotypic-phenotypic correlations in special histologic subtypes of BC inform diagnostic and therapeutic approaches, highlighting the significance of thoroughly comprehending BC heterogeneity.

Neuroendocrine Neoplasms of the Breast: Current Insights and Future Directions

BACKGROUND

The breast neuroendocrine neoplasms (NENs) represent a heterogeneous group of tumors and account for less than 1% of all NENs. The 5th edition of the WHO Classification of Breast Tumors in 2019 introduced a more stringent definition for breast NENs including neuroendocrine tumors (NETs) (G1, G2) and neuroendocrine carcinomas (NECs) (small cell carcinoma, large cell neuroendocrine carcinoma). While the diagnostic criteria and treatment of breast NENs still have some unsolved issues.

OBJECTIVE

We aim to discuss the diagnosis, treatment progress, existing problems, and future development direction of breast NENs.

METHODS

We provide a comprehensive review and evaluation of the diagnostic criteria, pathological features, utilization of immunohistochemical markers, molecular characteristics, pathogenesis, clinical significance, treatment options for breast NENs.

RESULTS

(1) Under the new definition, "pure" breast NENs are extremely rare. (2) Breast NETs are graded according to Nottingham grading System. Grading criteria utilized in other systems for NENs, such as mitotic count, ki67 proliferation index, and necrosis, have not been applied to breast NENs. (3) The WHO has not yet acknowledged the existence of NET G3 clearly. (4) The expression of NE markers may differ in breast NECs. (5) The treatment of breast NENs is still based on IBCs-NST, and without any difference from invasive carcinoma with NE features. (6) The prognosis of breast NENs remains unclear, while the prognosis for NECs is significantly poorer than invasive breast carcinomas of no special type (IBCs-NST) has been confirmed.

CONCLUSION

Strict adherence to criteria is the key to correctly diagnose breast NENs with the exclusion of metastasis from other sites. Further exploration is required to determine the tissue origin of breast NENs and understand the pathogenesis. Efforts are still needed to establish unified diagnostic criteria and a unique diagnosis and treatment consensus for breast NENs.

RB1 Genetic Alterations in Estrogen Receptor-Positive Breast Carcinomas: Correlation With Neuroendocrine Differentiation

Genetic alterations in the retinoblastoma susceptibility gene (RB1) are present in up to 40% of triple-negative breast cancers (BCs) and frequent in tumors with neuroendocrine differentiation, including small cell neuroendocrine carcinoma. Data on RB1 genetic alterations in estrogen receptor (ER)-positive BCs are scarce. In this study, we sought to define the morphologic, immunohistochemical, and genetic features of ER-positive BCs harboring somatic alterations in RB1, with emphasis on neuroendocrine differentiation. ER-positive BCs with pathogenic RB1 genetic alterations were identified in <1% of cases (N = 55) from a cohort of 6026 BCs previously subjected to targeted next-generation sequencing, including 23 primary BCs (pBCs) and 32 recurrent/metastatic BCs (mBCs). In cases where loss of heterozygosity of the wild-type RB1 allele could be assessed (93%, 51/55), most pBCs (82%, 18/22) and mBCs (90%, 26/29) exhibited biallelic RB1 inactivation, primarily through loss-of-function mutation and loss of heterozygosity (98%, 43/44). Upon histologic review, a subset of RB1-altered tumors exhibited neuroendocrine morphology (13%, 7/55), which correlated with expression of neuroendocrine markers (39%, 9/23) in both pBCs (27%, 3/11) and mBCs (50%, 6/12). Loss of Rb protein expression was observed in BCs with biallelic RB1 loss only, with similar frequency in pBCs (82%, 9/11) and mBCs (75%, 9/12). All cases with neuroendocrine marker expression (n = 9) and/or neuroendocrine morphology (n = 7) harbored biallelic genetic inactivation of RB1 and exhibited Rb loss of expression. TP53 (53%, 29/55) and PIK3CA (45%, 25/55) were the most frequently comutated genes across the cohort. Overall, these findings suggest that ER-positive BCs with biallelic RB1 genetic alterations frequently exhibit Rb protein loss, which correlates with neuroendocrine differentiation in select BCs. This study provides insights into the molecular and phenotypic heterogeneity of BCs with RB1 genetic inactivation, underscoring the need for further research into the potential clinical implications associated with these tumors.

Comparison of clinical characteristics and outcomes in primary neuroendocrine breast carcinoma versus invasive ductal carcinoma

Background

Neuroendocrine breast carcinoma (NECB) is a rare, special histologic type of breast cancer. There are some small sample studies on the clinical outcomes of NECB patients, which are worthy of further discussion.

Methods

We conducted a retrospective case-control study of clinical characteristics and outcomes among patients with primary NECB versus invasive carcinoma of no special type (NST) between November 2004 and November 2017 in the Peking Union Medical College Hospital, Beijing. NST patients were strictly matched 1:4 during the same period based on the TNM stage. Statistical comparisons were performed to determine the differences in survival between NST and NECB patients and to identify clinical factors that correlate with prognosis.

Results

A total of 121 participants affected by primary NECB were included in our analysis from November 2004 to November 2017. Elderly persons (>60 years of age) were more likely to have primary NECB than young persons (p=0.001). In addition, primary NECB patients had significantly higher odds of having tumors 2-5 cm (36.5%) and >5 cm (6.1%) in size than NST patients. Despite a significant difference in tumor size, the proportion of patients with lymph node metastases showed no difference between the two groups (p=0.021). In addition, the rate of patients with ER-negative tumors in the NECB group (4.2%) was significantly lower than that in the primary NST group (29.8%). Significant differences were noted in the PR-negative (13.3% versus 36.6%, P<0.001) and HER2-negative (90.5% versus 76.4%, P=0.001) expression statuses among these patients. Of 121 primary NECB patients, 11 (9.1%) experienced relapses during the follow-up period. We found that tumor size was an independent risk factor for relapse. For hormone receptors on tumor cells, ER-positive breast cancer patients had significantly lower odds of relapse than receptor-negative patients.

Conclusions

Our data demonstrate no significant difference in mortality and relapse between the primary NECB and NST groups. The tumor size in the primary NECB group was significantly larger than that in the NST group. In addition, the absence of ER independently increased the relapse rate for breast carcinoma patients.

Intraductal papilloma with atypical ductal hyperplasia and neuroendocrine differentiation as a possible precursor lesion of solid papillary carcinoma

Breast papillary neoplasms include a wide range of tumor types, and their pathological diagnosis is sometimes difficult. Furthermore, the etiology of these lesions is still not fully understood. We report the case of a 72-years-old woman referred to our hospital with bloody discharge from the right nipple. An imaging study detected a cystic lesion, including a solid component contiguous with the mammary duct, in the subareolar region. The lesion was then removed by segmental mastectomy. Pathological examination of the resected specimen revealed an intraductal papilloma with atypical ductal hyperplasia. Moreover, the atypical ductal epithelial cells expressed neuroendocrine markers. The presence of an intraductal papillary lesion with neuroendocrine differentiation suggests solid papillary carcinoma. Thus, this case suggests that intraductal papilloma could be a precursor of solid papillary carcinoma.

Deep and Repeated Response to Trastuzumab Deruxtecan in a Patient With Human Epidermal Growth Factor Receptor 2-Amplified Large-Cell Neuroendocrine Carcinoma With Brain Metastases: A Case Report

Metastatic CUP is complex, especially NCUP. Precision oncology is crucial for rare, aggressive cancers. A 54-year-old had HER2+ neuroendocrine carcinoma of unknown origin. T-DXd treatment, response, re-challenge show importance of genomics and caution.

Comparison of the mutational profiles of neuroendocrine breast tumours, invasive ductal carcinomas and pancreatic neuroendocrine carcinomas

The pathophysiology and the optimal treatment of breast neuroendocrine tumours (NETs) are unknown. We compared the mutational profiles of breast NETs (n = 53) with those of 724 publicly available invasive ductal carcinoma (IDC) and 98 pancreatic NET (PNET) cases. The only significantly different pathogenetic or unknown variant rate between breast NETs and IDCs was detected in the TP53 (11.3% in breast NETs and 41% in IDCs, adjusted p value 0.027) and ADCK2 (9.4% in breast NETs vs. 0.28% in IDCs, adjusted p value 0.045) genes. Between breast NETs and PNETs, different pathogenetic or unknown variant frequencies were detected in 30 genes. For example, MEN1 was mutated in only 6% of breast NETs and 37% in PNETs (adjusted p value 0.00050), and GATA3 pathogenetic or unknown variants were only found in 17.0% of breast NETs and 0% in PNETs (adjusted p value 0.0010). The most commonly affected oncogenic pathways in the breast NET cases were PI3K/Akt/mTOR, NOTCH and RTK-RAS pathways. Breast NETs had typically clock-like mutational signatures and signatures associated with defective DNA mismatch repair in their mutational landscape. Our results suggest that the breast NET mutational profile more closely resembles that of IDCs than that of PNETs. These results also revealed several potentially druggable targets, such as MMRd, in breast NETs. In conclusion, breast NETs are indeed a separate breast cancer entity, but their optimal treatment remains to be elucidated.