Concordance between pathologists and between specimen types in detection of HER2-low breast carcinoma by immunohistochemistry.

CONTEXT: Recent clinical trials indicate that HER2-targeted therapy may benefit HER2-low breast cancer patients including HER2 score 1+ or 2+ and no gene amplification. Concordance between pathologists and between core biopsy and surgical excision in establishing HER2-low status was evaluated. DESIGN: 57 patients with HER2 negative breast cancer (IHC 0, 1+, or 2+, no gene amplification) by core biopsy were included. Core biopsy and representative tumor from corresponding surgical excision was immunostained for HER2. Original HER2 IHC scores were interpreted using 2018 guidelines. Three pathologists independently interpreted again under 2023 guidelines. Kappa statistic evaluated agreement of HER2 IHC scores. RESULTS: Applying 2023 guidelines, HER2 IHC scores were concordant among study pathologists in 46 of 57 (81 %) core biopsy and 50 of 57 (88 %) surgical resections. Kappa statistics were 0.78 and 0.85 (substantial agreement), for inter-pathologist agreement of core biopsy and surgical resections under 2023 guidelines; 0.55 (moderate agreement) for agreement between first interpretation by 2018 guidelines and second interpretation by 2023 guidelines; and 0.13 (slight agreement) for agreement in HER2 consensus scores between outside core and surgical resection and 0.49 (moderate agreement) for inside core and surgical resection. Low HER2 expression was found in 28 of 57 (49 %) core biopsy and in 25 of 57 (44 %) surgical excisions. CONCLUSIONS: Interobserver agreement among study pathologists was good in core biopsy and surgical excisions, applying updated 2023 guidelines. Intratumoral heterogeneity in protein expression and preanalytical factors may result in variable identification of HER2-low status in core biopsy and surgical excision specimens.

Tumour budding in invasive breast carcinoma of no special type - relationship with clinicopathological parameters.

Each breast cancer is a heterogeneous tumour with different clinicopathological feature, and thus they all have different prognoses. Tumour budding (TB), considered as the first step in tumour metastasis, is the most critical factor for poor prognosis and is associated with the epithelial-mesenchymal transition (EMT). Tumour budding and its clinicopathological features in invasive breast carcinoma of no special type (NST). Patients who underwent surgery for invasive breast carcinoma (NST) between January 2018 and 2022 were retrospectively reviewed from the database, haematoxylin and eosin-stained slides were retrieved and reevaluated. The study included 200 patients. The mean number of TB was 12.8 ±9.6. The number of TB was significantly lower in patients who underwent neoadjuvant chemotherapy treatment ( p = 0.002). There was a weak positive correlation between TB count and tumour size ( r = 0.177). Triple-negative patients had significantly lower TB counts ( p = 0.001). No significant difference was observed between histological grade, nuclear grade, presence of ductal carcinoma in situ , stromal tumour-infiltrating lymphocytes, perineural invasion, lymph node metastasis, and number of TB ( p > 0.05). The number of TB was higher in oestrogen receptor positive tumours ( p = 0.015). There were more TB in patients with angiolymphatic invasion, which supports the pathophysiological relationship between tumour budding, metastasis, and EMT. Clarification of the mechanism of TB with more studies is promising in terms of treatment options.

Subtypes of high-grade breast ductal carcinoma in situ (DCIS): incidence and potential clinical impact.

OBJECTIVE: The purpose of this study was to investigate and classify the molecular subtypes of high-grade ductal carcinoma in situ (DCIS) and identify possible high-risk subtypes. The heterogenicity of DCIS with variable clinical and histopathological presentations has been recognized. Nevertheless, only histopathological grading and diameter are currently implemented in clinical decision-making following the diagnosis of DCIS. The molecular subtypes of DCIS and their IHC surrogate markers have not been defined in conventional treatment guidelines and recommendations. We applied the definitions of molecular subtypes according to the IHC surrogate markers defined for IBC and subclassified high-grade DCIS, accordingly. METHODS: Histopathological specimens were collected, revised, and regraded from 494 patients diagnosed with DCIS between 1996 and 2018. Other in situ and papillary lesions observed in breast biopsies were excluded from this study. 357 high-grade DCIS cases were submitted to IHC analysis. The markers investigated were ER, PR, HER2, and Ki67. RESULTS: 45 cases were classified as grade 1, 19 as grade 2, and 430 as grade 3. Sixty patients with high-grade DCIS had an additional invasive component in the surgical specimen. Thirty-three patients were diagnosed with recurrent DCIS or invasive cancer (minimum one year after their primary DCIS diagnosis). The proportions of luminal A and luminal B HER2-negative subtypes varied depending on whether 2011 or 2013 St. Gallen Consensus Conference guidelines were adopted. Luminal A was the most prevalent subtype, according to both classifications. The luminal B HER2-positive subtype was found in 22.1% of cases, HER2-enriched subtype in 21.8%, and TPN subtype in 5.6%. There were strong indications that HER2-enriched subtype was significantly more frequent among DCIS with invasive component (p = 0.0169). CONCLUSIONS: High-grade DCIS exhibits all the molecular subtypes previously identified in IBC, but with a somewhat different distribution in our cohort. HER2-enriched subtype is substantially related to the presence of an invasive component in DCIS; consequently, it is regarded as a high-risk entity.

Investigating the role of core needle biopsy in evaluating tumor-stroma ratio (TSR) of invasive breast cancer: a retrospective study.

PURPOSE: Tumor-stroma ratio (TSR) of invasive breast carcinoma has gained attention in recent years due to its prognostic significance. Previous studies showed TSR is a potential biomarker for indicating the tumor response to neoadjuvant chemotherapy. However, it is not clear how well TSR evaluation in biopsy specimens might reflect the TSR in resection specimens. We conducted a study to investigate whether biopsy evaluation of TSR can be an alternative method. METHOD: We collected cases with invasive breast carcinoma of no special type (IBC-NST) from University of Yamanashi hospital between 2011 and 2017 whose biopsy and resection specimens both had a pathologically diagnosis of IBC-NST (n = 146). We conceptualized a method for evaluating TSR in biopsy specimens within a preliminary cohort (n = 50). Within the studied cohort (n = 96), biopsy-based TSR (b-TSR) and resection-based TSR (r-TSR) were scored by two pathologists. We then evaluated our method's validity and performance by measuring interobserver variability between the two pathologists, Spearman's correlation between b-TSR and r-TSR, and the receiver operating characteristics (ROC) analysis for defining stroma-rich and stroma-poor tumors. RESULTS: Intra-class coefficient between the two pathologists was 0.59. The correlation coefficients between b-TSR and r-TSR in the two pathologists were 0.45 and 0.37. The ROC areas under the curve were 0.7 and 0.67. By considering an r-TSR of < 50% as stroma-rich, the sensitivity and specificity of detecting stroma-rich tumors were 64.1% and 66.7%, respectively, when b-TSR was < 40%. CONCLUSION: Our current b-TSR evaluation method can provide information about r-TSR and facilitate pre-treatment therapy follow-up.

The prognostic significance of non-lymphoid immune cells of the tumor microenvironment, including neutrophils, eosinophils, and mast cells in breast carcinomas.

BACKGROUND AND OBJECTIVE: The prognostic importance of lymphoid cells in the tumor microenvironment and their effect on treatment response have been demonstrated in many cancer types. However, there are limited studies on non-lymphoid immune cells. Conflicting results have been obtained regarding the effects of these cells on prognosis. MATERIALS AND METHODS: A total of 331 patients who underwent surgery for breast cancer were included. Patients that received neoadjuvant chemotherapy and those with distant metastasis were excluded. CD 15 immunohistochemistry was performed to detect tumor-infiltrating neutrophils (TINs) and eosinophils (TIEs), while Toluidine Blue histochemistry was performed to detect tumor-infiltrating mast cells (TIMs). RESULTS: High TINs were statistically associated with low ER expression (p < 0.001), low PR expression (p = 0.001), high Ki-67 proliferation index (p = 0.008), and HER2/TN molecular subtypes (p = 0.001). High TIEs were associated with low ER expression (p = 0.001), high Ki67 proliferation index (p = 0.005), and HER2/TN molecular subtype (p = 0.002). High TIMs were associated with high PR expression (p = 0.024), low Ki-67 proliferation index (p = 0.003), and high survival rate (p = 0.006). TIMs and TIEs were good prognostic factors for overall survival in Luminal A and Luminal B subtypes, while TINs and TIEs were found to be independent risk factors for disease-free survival. CONCLUSION: The evaluation of components of the tumor microenvironment including TINs, TIEs, and TIMs is easy and practical. High TIMs and TIEs are independent prognostic factors, especially in luminal molecular subtype of invasive breast carcinoma. However, to use this parameter in routine pathology practice, more studies from different centers and standard evaluation are needed.

ASAP1 Expression in Invasive Breast Cancer and Its Prognostic Role.

Breast cancer is a major global health burden with high morbidity and mortality rates. Previous studies have reported that increased expression of ASAP1 is associated with poor prognosis in various types of cancer. This study was conducted on 452 breast cancer patients who underwent surgery at Hanyang University Hospital, Seoul, South Korea. Data on clinicopathological characteristics including molecular pathologic markers were collected. Immunohistochemical staining of ASAP1 expression level were used to classify patients into high and low groups. In total, 452 cases low ASAP1 expression group was associated with significantly worse recurrence-free survival (p = 0.029). In ER-positive cases (n = 280), the low ASAP1 expression group was associated with significantly worse overall survival (p = 0.039) and recurrence-free survival (p = 0.029). In multivariate cox analysis, low ASAP1 expression was an independent significant predictor of poor recurrence-free survival in the overall patient group (hazard ratio = 2.566, p = 0.002) and ER-positive cases (hazard ratio = 4.046, p = 0.002). In the analysis of the TCGA dataset, the low-expression group of ASAP1 protein demonstrated a significantly poorer progression-free survival (p = 0.005). This study reports that low ASAP1 expression was associated with worse recurrence-free survival in invasive breast cancer.

Multi-omics analyses provide novel biological insights to distinguish lobular ductal types of invasive breast cancers.

BACKGROUND: Invasive lobular carcinoma (ILC) treatment is similar to invasive ductal carcinoma (IDC; now invasive carcinoma-no special type, IBC-NST), based on its intrinsic subtype. However, further investigation is required for an integrative understanding of differentially perturbed molecular patterns and pathways in these histotypes. METHODS: A dataset of 780 IDC and 201 ILC samples from the TCGA-BRCA project for cross-platform multi-omics was analyzed. We leveraged a consensus approach integrating different bioinformatic algorithms to analyze mutations, CNAs, mRNA, miRNA abundance, methylation, and protein abundance to understand the complex crosstalks that distinguish ILC and IDC samples. A histotype-matched comparison was performed. We performed Cox survival analyses for prognosis based on our identified 53 histotype-specific and four discordant genes. RESULTS: Approximately 90% of ILC cases were of the luminal subtype. Somatic mutations in CDH1 were higher in ILC than in IDC (FDR-adjusted p < 0.01). Fifty-three significant oncogenic or tumor-suppressive DEGs were identified in a single histotype. PPAR signaling and lipolysis regulation in adipocytes were significantly enriched in ILC tumors. CDH1 protein had the highest differential abundance (AUC: 0.85). Moreover, BTG2, GSTA2, GPR37L1, and PGBD5 amplification was associated with poorer OS in ILC compared with no alteration. RIMS2, NACA4P, MYC, ZFPM2, and POU5F1B amplification showed a lower overall survival in patients with IDC. miR-195 showed an IDC-specific downregulation, causing overexpression of CCNE1. Integrative multi-omics supervised analysis identified 296 differentially expressed genes that successfully distinguished IDC and ILC histotypes. CONCLUSIONS: Our findings identify novel molecular candidates that potentially drive and modify the disease differentially among these histotypes.

[Correlations of Androgen Receptor Expression with Molecular Subtypes and Clinopathological Features of Invasive Breast Carcinoma of No Special Type in Tibet].

Objective To investigate the expression of androgen receptor(AR)and its correlations with different molecular subtypes and clinicopathological features of breast invasive carcinoma of no special type(IBC-NST)in females of Tibetan ethnic minority in Tibet.Methods This study enrolled 54 female patients of Tibetan ethnic minority with IBC-NST surgically removed in the Tibet Autonomous Region People's Hospital from December 2015 to March 2021 for retrospective analysis.The clinical and pathological data of all the enrolled patients were collected.The immunohistochemical method was employed to determine the expression of AR,cell proliferation marker antigen (Ki-67),estrogen receptor(ER),human epidermal growth factor receptor 2(HER-2),and progesterone receptor(PR).For those with unclear HER-2 results,fluorescence in situ hybridization was employed for the determination.The relationship of AR expression with molecular subtypes and clinicopathological features was then analyzed.Results The expression of AR in Tibetan female patients with IBC-NST was correlated with ER(χ2=8.200,P=0.004),PR(χ2=9.900,P=0.003),and molecular subtype(χ2=11.690,P=0.009)and not correlated with tumor location,age,size,histological grade,lymph node metastasis,vascular invasion,clinical stage,or expression of HER-2 and Ki-67(all P>0.05).Molecular subtype was correlated with histological grade(χ2=24.970, P=0.001),clinical stage(χ2=9.035, P=0.029),and lymph node metastasis(χ2=9.691,P=0.021).Conclusions The positive expression rate of AR in the triple-negative IBC-NST patients of Tibetan ethnic minority was significantly lower than that in ER-or PR-positive patients in Tibet.Molecular subtype was correlated with histological grade,clinical stage,and lymph node metastasis.

Tumor suppressor OTUD3 induces growth inhibition and apoptosis by directly deubiquitinating and stabilizing p53 in invasive breast carcinoma cells.

BACKGROUND: P53 pathway inactivation plays an important role in the process of breast cancer tumorigenesis. Post-translational protein modification abnormalities have been confirmed to be an important mechanism underlying inactivation of p53. Numerous deubiquitinating enzymes are aberrantly expressed in breast cancer, and a few deubiquitination enzymes can deubiquitinate and stabilize p53. Here, we report that ovarian tumor (OTU) deubiquitinase 3 (OTUD3) is a deubiquitylase of p53 in breast carcinoma (BC). METHODS: Correlations between the mRNA expression levels of OTUD3, TP53 and PTEN and the prognosis of BC were assessed with the Kaplan-Meier Plotter tool. OTUD3 protein expression in 80 pairs of specimens in our cohort was examined by immunohistochemistry and western blotting. The relationship among OTUD3, p53, and p21 proteins was analyzed. Half-life analysis and ubiquitylation assay were performed to elucidate the molecular mechanism by which OTUD3 stabilizes p53. The interaction between OTUD3 and p53 in BC cells was verified by a co-immunoprecipitation assay and GST pulldown experiments. MTS assay for proliferation detection, detection of apoptosis induced by cisplatin and colony formation assay were employed to investigate the functional effects of OTUD3 on breast cancer cells. RESULTS: OTUD3 downregulation is correlated with a poor prognosis in BC patients. OTUD3 expression is decreased in breast cancer tissues and not associated with the histological grade. OTUD3 also inhibits cell proliferation and clone formation and increases the sensitivity of BC cells to apoptosis induced by chemotherapy drugs. Reduced OTUD3 expression accompanied by decreased p53 abundance is correlated with human breast cancer progression. Ectopic expression of wild-type OTUD3, but not its catalytically inactive mutant, stabilizes and activates p53. Mechanistically, OTUD3 interacts directly with p53 through the amino-terminal OTU region. Finally, OTUD3 protects p53 from murine double minute 2 (Mdm2)-mediated ubiquitination and degradation, enabling the deubiquitination of p53 in BC cells. CONCLUSIONS: In summary, we found that OTUD3 may be a potential therapeutic target for restoring p53 function in breast cancer cells and suggest that the OTUD3-p53 signaling axis may play a critical role in tumor suppression.

"HER2 immunohistochemistry inter-observer reproducibility in 205 cases of invasive breast carcinoma additionally tested by ISH" Answer to the statistical issue to avoid misinterpretation.

Assessment of HER2 biomarker in invasive breast carcinoma patients allows a specific therapeutic approach. Clinical guidelines indicate immunohistochemistry (IHC) and in situ hybridization (ISH) to test HER2, however both have drawbacks which results in low reproducibility of results especially in equivocal cases. Our main objective is to quantify inter-observer IHC reproducibility and cross it with the ISH result. Our series includes 205 invasive breast carcinoma cases sent for ISH retest from 14 hospitals, 5 observers to assess the IHC and 1 observer for ISH of each case. We found that the observers only achieve an absolute agreement for IHC in 1 out of 3 cases. The inter-observer concordance for IHC is low (0.2 ≤ k ≤ 0.4) or moderate (0.41 ≤ k ≤ 0.6). In ISH positive cases the concordance for IHC is higher than in the ISH negative cases. In conclusion, the study shows low and moderate IHC inter-observer concordance, finding the more worrying values among the ISH negative cases which are the most part of this particular sample. Subjective interpretation of the techniques, among other factors, has negative impact in HER2 evaluation. To offset this limitation we have checked that reaching a consensus from different observers for HER2 IHC assessment improves the results.

HER2 immunohistochemistry inter-observer reproducibility in 205 cases of invasive breast carcinoma additionally tested by ISH.

Assessment of HER2 biomarker in invasive breast carcinoma patients allows a specific therapeutic approach. Clinical guidelines indicate immunohistochemistry (IHC) and in situ hybridization (ISH) to test HER2, however both have drawbacks which results in low reproducibility of results especially in equivocal cases. Our main objective is to quantify inter-observer IHC reproducibility and cross it with the ISH result. Our series includes 205 invasive breast carcinoma cases sent for ISH retest from 14 hospitals, 5 observers to assess the IHC and 2 observers for the ISH of each case. We found that the observers only achieve an absolute agreement for IHC in 1 out of 3 cases. The inter-observer concordance for IHC is low (0.2 ≤ k ≤ 0.4) or moderate (0.41 ≤ k ≤ 0.6). In ISH positive cases the concordance for IHC is higher than in the ISH negative cases. In conclusion, the study shows low and moderate IHC inter-observer concordance, finding the more worrying values among the ISH negative cases which are the most part of this particular sample. Subjective interpretation of the techniques, among other factors, has negative impact in HER2 evaluation. To offset this limitation we have checked that reaching a consensus from different observers for HER2 IHC assessment improves the results.

Influence of HLDF Differentiation Factor on Nonspecific Invasive Breast Carcinoma in vitro.

The study was carried out on samples of invasive breast carcinoma of no special type from 36 patients aged 48.0 to 62.8 years. The effect of HLDF on nonspecific invasive breast carcinoma was a decrease in the relative content of low-differentiated cells and an increase in the relative content of highly differentiated cells. HLDF did not have a cytotoxic effect leading to the death of low-differentiated cells but promoted promotes the acquisition of a higher degree of differentiation by them. A more pronounced effect of HLDF was observed in more aggressive metastasizing forms of neoplasia, which allows us to consider this differentiation factor as a candidate for use in the differentiation therapy of malignant neoplasms.

Patient Selection for Ductal Carcinoma In Situ Observation Trials: Are the Lesions Truly Low Risk?

OBJECTIVE: The purpose of this article is to report on a study conducted to determine whether the lesions in patients with what is deemed to be low-risk ductal carcinoma in situ (DCIS) selected for two large clinical trials are in fact low-risk lesions. CONCLUSION: A retrospective review was conducted to determine whether the eligibility criteria of the two trials are predictive that DCIS is low risk. More than 20% of lesions are upgraded to invasive carcinoma in patients with low-risk DCIS as defined in two large clinical trials. More accurate methods are needed to determine whether patients with a diagnosis of low-grade DCIS can be treated less aggressively.

Significance of Matrix Metalloproteinase 9 Expression as Supporting Marker to Cytokeratin 19 mRNA in Sentinel Lymph Nodes in Breast Cancer Patients.

One-step nucleic acid amplification (OSNA) detects and quantifies, with the use of a polymerase chain reaction, the presence of cytokeratin 19 mRNA in sentinel lymph nodes. The main advantage of the OSNA assay is the avoidance of second surgery in case of positive sentinel lymph node diagnosis. The objective of this study was to evaluate the significance of matrix metalloproteinase 9 expression by immunohistochemistry as supporting marker to cytokeratin 19 mRNA in sentinel lymph nodes in breast cancer patients and to relate this expression with clinicopathological data. This study was conducted on fresh sentinel lymph nodes obtained from 40 patients with tumors classified as carcinoma of no special type. The presence of metastatic cells in the slices of lymph nodes was evaluated by immunohistochemistry using antibodies for CK19 and MMP-9. Expression of CK19 and MMP-9 in lymph nodes was also confirmed by means of Western blot analysis. Results indicated that the strongest correlation with CK19 mRNA was displayed by MMP-9, CK19 (by immunohistochemistry, IHC), and nodal metastases (p < 0.001). Higher histological grading also positively correlated with CK19 mRNA, however that correlation was less significant. Since MMP-9 shows very strong correlation with CK19 mRNA in breast carcinoma of no special type metastases, expression of MMP-9 in sentinel lymph nodes should be considered as useful method whenever OSNA analysis is not available.

BRCA-mutated Invasive Breast Carcinomas: Immunohistochemical Analysis of Insulin-like Growth Factor II mRNA-binding Protein (IMP3), Cytokeratin 8/18, and Cytokeratin 14.

To evaluate the expression of insulin-like growth factor II mRNA-binding protein (IMP3), CK8/18, and CK14 in BRCA mutated and sporadic invasive breast carcinoma. Immunohistochemistry for IMP3, CK8/18, and CK14 was performed on 39 cases of invasive breast carcinomas with BRCA mutation (24 BRCA1, 14 BRCA2, and 1 dual BRCA1/BRCA2) and 54 cases of sporadic invasive breast carcinomas. The relationship between the IMP3, CK8/18, and CK14 and the tumor grade and molecular phenotypes were analyzed. IMP3, CK8/18, and CK14 positivity were present in 20 (51%), 22 (56%), and 14 (36%) of 39 BRCA-mutated breast carcinomas, and 11 (20%), 53 (98%), and 24 (44%) of 54 sporadic breast carcinomas respectively. The rates of IMP3 expression and absence of CK8/18 (44% versus 2%) in BRCA-mutated breast carcinomas was significantly higher than the sporadic breast carcinomas (p = 0.002 and p < 0.001). No significant difference was observed for CK14 among the two groups (p = 0.408). No significant difference was observed among BRCA1-related and BRCA2-related breast carcinomas in the immunoprofile for IMP3, CK8/18, and CK14. No significant correlation was identified between the expression of IMP3 and CK8/18 and the tumor grade in both BRCA-mutated and sporadic breast carcinomas (p > 0.05). In cases with luminal A and B phenotypes, the rates of expression of IMP3 and loss of CK8/18 were significantly higher in BRCA-mutated as compared to sporadic breast carcinoma (p < 0.001). In cases with basal-like phenotype, the absence of CK8/18 expression was significantly higher in BRCA-mutated breast carcinomas (54% versus 0%, p = 0.001), while no difference was observed for IMP3 expression (p = 0.435). Regardless of mutation type, histologic grade, or molecular phenotype, the absence of CK8/18 expression and presence of IMP3 expression are seen at much higher rate in BRCA mutated breast carcinomas.

Noninvasive Assessment of Tumor Histological Grade in Invasive Breast Carcinoma Based on Ultrasound Radiomics and Clinical Characteristics: A Multicenter Study.

Rationale and Objectives: We aimed to develop and validate prediction models for histological grade of invasive breast carcinoma (BC) based on ultrasound radiomics features and clinical characteristics. Materials and Methods: A number of 383 patients with invasive BC were retrospectively enrolled and divided into a training set (207 patients), internal validation set (90 patients), and external validation set (86 patients). Ultrasound radiomics features were extracted from all the eligible patients. The Boruta method was used to identify the most useful features. Seven classifiers were adopted to developed prediction models. The output of the classifier with best performance was labeled as the radiomics score (Rad-score) and the classifier was selected as the Rad-score model. A combined model combining clinical factors and Rad-score was developed. The performance of the models was evaluated using receiver operating characteristic curve. Results: Seven radiomics features were selected from 788 candidate features. The logistic regression model performing best among the 7 classifiers in the internal and external validation sets was considered as Rad-score model, with areas under the receiver operating characteristic curve (AUC) values of 0.731 and 0.738. The tumor size was screened out as the risk factor and the combined model was developed, with AUC values of 0.721 and 0.737 in the internal and external validation sets. Furthermore, the 10-fold cross-validation demonstrated that the 2 models above were reliable and stable. Conclusion: The Rad-score model and combined model were able to predict histological grade of invasive BC, which may enable tailored therapeutic strategies for patients with BC in routine clinical use.

Mucinous Carcinoma of the Breast With Neuroendocrine Differentiation: A Case Report of Cyto-Histopathology Findings.

Mucinous breast carcinoma is a rare neoplasm. A minority of breast neoplasms exhibit a mucinous component, with purely mucinous cases being less frequent. It is more typically found in postmenopausal women. The etiology is multifactorial and involves dietary factors, reproductive factors, and hormonal factors. Mucinous carcinoma can grow to a large size at the time of diagnosis, although it typically grows slowly and palpable. Transcriptomic genetic studies have explained that mucinous tumors are of luminal A molecular subtype. Mucinous A tumors have different transcriptome characteristics than mucinous B tumors, which have a gene expression pattern resembling neuroendocrine (NE) carcinomas. Diagnosis of mucinous carcinoma with NE differentiation by fine needle aspiration cytology (FNAC) is reported infrequently. Histopathology is mandatory in the evaluation of mucinous breast carcinoma. NE carcinoma of the breast is an underestimated subtype of BC which has characteristics of heterogenicity, rarity, and poor differentiation. In this instance, we present a case of breast carcinoma exhibiting NE differentiation. A postmenopausal woman aged 63, with no family history of breast cancer, presented with a firm mass in the upper lateral quadrant of her right breast. This lump, causing discomfort for the past two years, was accompanied by nipple retraction and the discharge of bloody fluid. The clinical examination revealed the palpable presence of the lump. Ultrasonography-guided FNAC suggested Mucinous breast carcinoma with NE differentiation. The patient underwent a modified radical mastectomy, and the tissue was evaluated by immunohistochemistry which confirmed the diagnosis.

Unusual Case of Papillary Carcinoma of the Breast.

Papillary carcinoma of the breast represents a distinct subtype of breast cancer characterized by its unique clinical and histopathological features. It is seen predominantly affecting post-menopausal women. Overall, papillary carcinoma has a low prevalence. Histologically, papillary carcinoma is characterized by the presence of papillae-like structures lined by epithelial cells and supported by fibrovascular cores, appearing like a dual-layered epithelium. The clinical, epidemiological, and pathological characteristics of papillary carcinoma of the breast are not widely described in the existing literature. The gold standard for diagnosis of carcinoma breast of any type remains a core needle biopsy, but in our case, the diagnosis of papillary carcinoma was made in the final histopathology specimen. Treatment strategies for papillary carcinoma include surgical excision with or without axillary dissection followed by adjuvant chemo-radiotherapy depending on the immunohistochemistry and tumor characteristics, but there appear multiple variations in the management of more common NOS (not otherwise specified) type and the papillary carcinoma of the breast. We present a case report of this papillary carcinoma of the breast.

Long-Lasting Complete Remission in a Patient With Metastatic Metaplastic Breast Cancer Treated With Immune Checkpoint Inhibitor and Chemotherapy: A Case Report and a Review of the Literature.

Metaplastic breast cancer (MpBC) is a rare form of breast cancer known for suboptimal response to chemotherapy, high recurrence rate, poor prognosis, and limited treatment options. Recent studies have reported that MpBC has high expression of programmed death ligand 1 and tumor-infiltrating lymphocytes, indicating the potential effectiveness of immunotherapy (IO) in MpBC. In addition, several reports have demonstrated the activity of IO in MpBC. In this case report, we present a case of recurrent MpBC that achieved durable, rapid, complete remission with atezolizumab (anti-PD-L1) and nab-paclitaxel with a continued response even after discontinued therapy.