Metaplastic breast cancer: a comparison between the most common histologies with poor immunohistochemistry factors

Translational Aspects in Metaplastic Breast Carcinoma

Breast cancer is the most common cancer among women. Metaplastic breast carcinoma (MpBC) is a rare, heterogeneous group of invasive breast carcinomas, which are classified as predominantly triple-negative breast carcinomas (TNBCs; HR-negative/HER2-negative). Histologically, MpBC is classified into six subtypes. Two of these are considered low-grade and the others are high-grade. MpBCs seem to be more aggressive, less responsive to neoadjuvant chemotherapy, and have higher rates of chemoresistance than other TNBCs. MpBCs have a lower survival rate than expected for TNBCs. MpBC treatment represents a challenge, leading to a thorough exploration of the tumor immune microenvironment, which has recently opened the possibility of new therapeutic strategies. The epithelial-mesenchymal transition in MpBC is characterized by the loss of intercellular adhesion, downregulation of epithelial markers, underexpression of genes with biological epithelial functions, upregulation of mesenchymal markers, overexpression of genes with biological mesenchymal functions, acquisition of fibroblast-like (spindle) morphology, cytoskeleton reorganization, increased motility, invasiveness, and metastatic capabilities. This article reviews and summarizes the current knowledge and translational aspects of MpBC.

Outcomes of Metaplastic Breast Cancer Versus Triple-Negative Breast Cancer: A Propensity Score Matching Analysis

PURPOSE

This study aims to compare the survival outcomes of metaplastic breast cancer (MPBC) with triple-negative breast cancer (TNBC) and identify prognostic factors that influence the survival outcomes of MPBC patients and TNBC patients.

METHODS

Patients with nonmetastatic MPBC or TNBC were reviewed from our database. Patients' clinicopathologic and molecular features were analyzed with respect to outcomes, including disease-free survival (DFS) and overall survival (OS). Propensity score matching (PSM) with a one-to-three matching between MPBC patients and TNBC patients was performed.

RESULTS

A total of 857 female patients (76 MPBC patients and 781 TNBC patients) were included in this study. A subgroup of triple-negative MPBC (n  =  60) was matched with TNBC (n  =  180) cases based on patient characteristics and treatments. Kaplan-Meier analysis indicated that the MPBC group was associated with worse OS and DFS before (P  =  0.0046 both) and after (P  =  0.011 and P  =  0.0046, respectively) PSM. Multivariable analysis revealed that a higher T stage (T > 2) (P  =  0.032) and higher lymph node stage (N3 vs. N0-2, P  =  0.012) were associated with worse OS after PSM. For DFS, the MPBC group (P  =  0.012), higher T stage (T > 2) (P  =  0.032), and higher lymph node stage (N3 vs. N0-2, P  =  0.045) were associated with worse DFS. Among the 76 MPBC patients, a higher T stage and mesenchymal differentiation were associated with worse OS (pT1/2 vs. pT3/4 and mesenchymal differentiation vs. other subtypes, P  =  0.007 and P  =  0.011, respectively).

CONCLUSIONS

Compared with TNBC, MPBC was associated with worse OS and DFS. Mesenchymal differentiation has a worse DFS than other subtypes of MPBC.

Metaplastic Breast Carcinoma: Clinicopathologic Features and Recurrence Score Results From a Population-based Database

OBJECTIVES

Metaplastic breast carcinoma (MBC) is a rare, aggressive form of cancer comprising epithelial and mesenchymal elements. The purpose of this study was to use population-based data to review the clinicopathologic, molecular features, and outcomes of MBC.

METHODS

Surveillance, Epidemiology, and End Results Program (SEER) data were used to identify MBC and invasive ductal carcinoma (IDC), no special type (NOS) between 2004 and 2015. Results from Oncotype DX's 21-gene assay linked to SEER registries were included for hormone receptor (HR)-positive tumors. χ 2 analysis was performed to determine the differences between MBC and IDC. Kaplan-Meier curves and multivariate Cox proportional hazards models were used for breast cancer specific death (BCSD).

RESULTS

Compared with IDC, NOS (n=509,864), MBC (n=3876) were more likely to present at an older age, be black, have negative lymph nodes, be >2 cm, grade 3, and triple negative (TN). All subtypes [HR-positive/human epidermal growth receptor 2 (HER2)-negative, HR-positive/HER2-positive, HR-negative/HER2-positive, and TN] had higher BCSD than IDC, NOS. 22.3% of MBC cases were HR-positive. HR-positive MBCs tested for a recurrence score (RS) 65% were high-risk compared with 16.8% of IDC, NOS. Within the MBC cohort, no significant differences in BCSD were identified with respect to different molecular subtypes. In a fully adjusted model, TN or HER2-positive status did not adversely affect BCSD compared with HR-positive MBC.

CONCLUSIONS

All molecular subtypes of MBC had a poorer prognosis compared with IDC, NOS. The different molecular subtypes of MBC did not affect the BCSD. HR-positive MBC patients had a significantly higher high-risk RS than IDC, NOS patients.

Metaplastic breast cancer: A review

Metaplastic breast cancer (MpBC) is an uncommon aggressive malignancy that is associated with a poor prognosis. Due to its rarity, the relationships between the clinical and pathological features of MpBC, treatment approach, and clinical outcomes remain underexplored. In the following review article, we synthesize the existing data on the clinical, pathological and genomic features, management, and outcomes of MpBC. We also identify potential targets for future clinical trials.

Metaplastic breast cancers and triple-negative breast cancers of no special type: are they prognostically different? A systematic review and meta-analysis

BACKGROUND AND AIMS

Metaplastic breast cancer (MBC) and triple-negative (TN) BC of no special type are often confounded with each other in terms of survival and prognosis. In this systematic study and meta-analysis, we evaluated the prognosis of each of these two different diagnoses.

METHODS

We conducted a systematic literature search and review using the MOOSE guidelines, through PUBMED database, the Ovid MEDLINE database, and the ISI Web of Science Citation Index Expanded (SCI Expanded). Overall survival (OS) and disease-free survival (DFS) were the main outcomes considered.

RESULTS

Our review eventually selected six independent studies, with a total of more than 59 519 patients. MBC was found to associate with worse OS compared to TNBC of no special type, with a significant 40% increased risk of death [summary hazard ratio (SHR) = 1.40, 95% confidence interval (CI): 1.30-1.50]. We found neither heterogeneity ( I2 = 0%) nor evidence of publication bias ( P = 0.82 and P = 0.49 by Begg's and Egger's test, respectively) between studies. No statistically significant difference was found between MBC and TNBC of no special type in terms of DFS (SHR = 1.17, 95% CI: 0.80-1.71).

CONCLUSION

This study demonstrates that TNBC of no special type and MBC have comparable DFS, although the latter presents a significantly worse prognosis in terms of OS. Despite DFS being similar in both subtypes, this did not result in significant OS benefits, with MBC score being the worse of the two diseases.

Metaplastic Breast Cancer: Characteristics and Survival Outcomes

Objectives

Metaplastic breast cancer (MBC) is a rare neoplasm accounting for <1% of all breast cancer. We evaluated the clinical characteristics and survival outcomes of MBC.

Methods

Patients diagnosed with pathologically proven MBC were reviewed from the institutional breast cancer database from 2000 to 2017.

Results

A total of 136 patients diagnosed with MBC were included in the study. The median age of the diagnosis was 60 years, and 60% of patients were stage II at diagnosis, and 22% were stage III. About two-thirds of the patients were triple-negative; 93% had nuclear grade III, and 25% had a lymphovascular invasion. Squamous differentiation (29%) was the most common histologic subtype, followed by the spindle subtype (21%). The most common distant metastases were lung (22%), followed by bone (13%). Moreover, 60% had a mastectomy, 19% had endocrine therapy, 58% had radiation, 51% received anthracycline-based chemotherapy, 26% had non-anthracycline chemotherapy, and 22% received no chemotherapy. In the entire cohort, the two-year overall survival (OS) and five-year OS were 79% and 69%, respectively, and the two-year progression-free survival (PFS) and five-year PFS were 72% and 61%, respectively. On multivariable analysis, the stage of MBC (stage III: hazard ratio (HR), 5.065 (95% confidence interval (CI), 1.02-25.27) (p=0.048)), poor functional status (Eastern Cooperative Oncology Group (ECOG) score, 2; HR, 24.736 (95% CI, 1.92-318.73) (p=0.014)), and distant metastasis to the brain (HR, 8.453 (95% CI, 1.88-38.04) (p=0.005)) and lung (HR, 42.102 (95% CI, 7.20-246.36) (p<0.001)) were significant predictors of decreased OS.

Conclusions

MBC demonstrated early disease progression and poor overall survival. The stage of MBC, decreased performance status, and metastasis to the lung and brain were independent poor prognostic factors.

Epithelial Mesenchymal Transition and Immune Response in Metaplastic Breast Carcinoma

Metaplastic breast carcinoma (MBC) is a heterogeneous group of infrequent triple negative (TN) invasive carcinomas with poor prognosis. MBCs have a different clinical behavior from other types of triple negative breast cancer (TNBC), being more resistant to standard chemotherapy. MBCs are an example of tumors with activation of epithelial–mesenchymal transition (EMT). The mechanisms involved in EMT could be responsible for the increase in the infiltrative and metastatic capacity of MBCs and resistance to treatments. In addition, a relationship between EMT and the immune response has been seen in these tumors. In this sense, MBC differ from other TN tumors showing a lower number of tumor-infiltrating lymphocytes (TILS) and a higher percentage of tumor cells expressing programmed death-ligand 1 (PD-L1). A better understanding of the relationship between the immune system and EMT could provide new therapeutic approaches in MBC.

Metaplastic breast cancer: Prognostic and therapeutic considerations

INTRODUCTION

Metaplastic breast cancer (MBC) is a rare condition of breast tumor with different subtypes, considered a disease with worse prognosis; treatments and survival are often unclear and conflicting.

METHODS

We consecutively collected 153 primary MBCs of different subtypes. Breast surgery, neoadjuvant or adjuvant treatment, clinic-pathological factors, number and type of events during follow-up were considered to evaluate overall survival (OS) and invasive disease-free survival (IDFS).

RESULTS

The majority of MBC was triple-negative (TN) subtype (88.7%), G3 (95.3%), pN0 (70.6%), and with high levels of Ki-67 (93.5%). For OS and IDFS, no significant associations were seen between the different MBC subtypes. The matched triple-negative MBC (TNMBC) and ductal TNBC cohorts had similar prognosis both in terms of OS (p = .411) and IDFS (p = .981). We observed a positive trend for TNMBC patients treated in the adjuvant setting with the cyclofosfamide, methotrexate, 5-fluorouracil protocol for better OS (p = .090) and IDFS (p = .087). A poor or absent response rate was observed in the neoadjuvant setting.

CONCLUSION

Our results demonstrate that metaplastic and ductal breast cancers with TN phenotype are similar in terms of overall and disease-free survival. Metaplastic cancers are poorly responsive to neoadjuvant treatment, and in the absence of novel targeted therapies, surgical treatment remains the first choice.

The longitudinal risk of mortality between invasive ductal carcinoma and metaplastic breast carcinoma

The management of metaplastic breast carcinoma (MBC) has largely paralleled the paradigms used for invasive ductal carcinoma (IDC) in the current National Comprehensive Cancer Network guidelines of breast cancer. However, patients with IDC and MBC have been shown to have a different prognosis, and there are significant differences in risk and failure patterns after treatment. The purpose of this study was to compare breast cancer specific survival (BCSS) and hazard function between IDC and MBC. We included patients from the Surveillance, Epidemiology, and End Results program with stage I-III IDC and MBC between 2000 and 2012. Statistical analyses were including chi-square analysis, life-table methods, multivariate Cox proportional hazards models, and propensity score matching (PSM). We identified 294,719 patients; 293,199 patients with IDC and 1520 patients with MBC. Multivariate analyses showed that the MBC subtype had significantly lower BCSS than the IDC subtype before and after PSM (p < 0.001). There were significant differences in the hazard curve between IDC and MBC. The hazard curve for breast cancer mortality in the IDC cohort peaked at 3 years (2%), and then changed to a slowly decreasing plateau after prolonged follow up. However, the hazard curve for breast cancer mortality in the MBC cohort peaked at 2 years (7%), then declined sharply between 3 and 6 years, and changed to a low death rate after a follow-up time exceeding 6 years. Subgroup analyses revealed that the hazard curves significantly differed between IDC and MBC after stratifying by tumor stage and hormone receptor status. Our study suggests that patients with MBC should receive more effective systemic agents and intensive follow-up because of their significantly augmented risk of death compared to IDC patients.

Molecular Features of Metaplastic Breast Carcinoma: An Infrequent Subtype of Triple Negative Breast Carcinoma

Metaplastic breast carcinoma (MBC) is a heterogeneous group of infrequent invasive carcinomas that display differentiation of the neoplastic epithelium towards squamous cells and/or mesenchymal-type elements. Most MBC have a triple negative phenotype and poor prognosis. Thus, MBC have worse survival rates than other invasive breast carcinomas, including other triple negative breast carcinomas (TNBC). In this study, we reviewed the molecular features of MBC, pointing out the differences among subtypes. The most frequently mutated genes in MBC were TP53 and PIK3CA. Additionally, mutations in the other genes of the PI3K/AKT pathway indicated its importance in the pathogenesis of MBC. Regarding copy number variations (CNVs), MYC was the most frequently amplified gene, and the most frequent gene loss affected the CDKN2A/CDKN2B locus. Furthermore, the pattern of mutations and CNVs of MBC differed from those reported in other TNBC. However, the molecular profile of MBC was not homogeneous among histological subtypes, being the alterations in the PI3K pathway most frequent in spindle cell carcinomas. Transcriptomic studies have demonstrated an epithelial to mesenchymal program activation and the enrichment of stemness genes in most MBC. In addition, current studies are attempting to define the immune microenvironment of these tumors. In conclusion, due to specific molecular features, MBC have a different clinical behavior from other types of TNBC, being more resistant to standard chemotherapy. For this reason, new therapeutic approaches based on tumor molecular characteristics are needed to treat MBC.

Prognosis in different subtypes of metaplastic breast cancer: a population-based analysis

BACKGROUND

Metaplastic breast cancer (MpBC) is a rare histological subtype of breast cancer recognized as a unique pathologic entity in 2000. However, the pathogenesis, optimal therapy, and prognosis of MpBC and the potential effect of systemic treatments on different subtypes of MpBC are not well defined.

METHODS

A retrospective population-based study was performed to identify breast cancer patients with MpBC and other triple-negative breast cancers (TNBC) between 2010 and 2014 using the surveillance, Epidemiology, and End Results (SEER) database. Chi-square test was used to analyze characteristics between subgroups. Kaplan-Meier analysis and Multivariate Cox regressions were used to evaluate overall survival (OS) of MpBC, TNBC, and MpBC subgroups. Competing risk analysis and multivariate regression model of competing risk were used to assess breast cancer-specific survival (BCSS) of MpBC and TNBC RESULTS: We identified a study cohort of 22,433 patients (1112 MpBC and 21,321 TNBC). MpBC correlated with older population, larger tumor size and less lymph node involvement, and TNBC phenotype. Patients with MpBC especially with triple-negative subtype (TN-MpBC) had worse survival than the overall TNBC population. However, the prognosis of MpBC without triple-negative subtype (non-TN MpBC) was not different from that of TNBC. In Kaplan-Meier analysis, chemotherapy was not associated with significant difference in OS of TN-MpBC. In non-TN MpBC group, the 3-year OS was 79.8% for patients receiving chemotherapy and 70.5% in patients without chemotherapy, and chemotherapy was associated (P = 0.033) with improved OS. Within the MpBC patients, radiotherapy was significantly (HR 1.544; 95% CI 1.148-2.078; P = 0.004) associated with improved OS and (HR 1.474; 95% CI 1.067-2.040; P = 0.019) BCSS.

CONCLUSIONS

Patients with TN-MpBC had worse prognosis than TNBC and chemotherapy was not associated with improved survival. In contrast, non-TN MpBC may derive survival benefit from chemotherapy and radiotherapy.

Metaplastic Breast Cancer Treatment and Outcomes in 2500 Patients: A Retrospective Analysis of a National Oncology Database

BACKGROUND

Metaplastic breast cancer (MBC) is characterized by chemoresistance and hematogenous spread. We sought to identify factors associated with improved MBC outcomes and increased likelihood of MBC diagnosis.

METHODS

Women ≥ 18 years of age with stage I-III MBC and non-MBC diagnosed between 2010 and 2014 were identified in the National Cancer Data Base. Kaplan-Meier and multivariate Cox proportional hazards models were used to estimate associations with overall survival (OS). Multivariate logistic regression identified factors associated with MBC diagnosis.

RESULTS

Overall, 2451 MBC and 568,057 non-MBC patients were included; 70.3% of MBC vs. 11.3% of non-MBC patients were triple negative (p < 0.001). Five-year OS was reduced among MBC vs. non-MBC patients for the entire cohort (72.7 vs. 87.5%) and among triple-negative patients (71.1 vs. 77.8%; both p < 0.001). In MBC, triple-negative (vs. luminal) subtype was not associated with worse OS (hazard ratio [HR] 1.16, 95% confidence interval [CI] 0.88-1.54, p = 0.28). Compared with non-MBC patients, MBC patients were more likely to receive mastectomy (59.0 vs. 44.9%), chemotherapy (74.1 vs. 43.1%), and axillary lymph node dissection (ALND; 35.2 vs. 32.2%, all p ≤ 0.001). MBC patients more frequently had negative ALND (pN0) than non-MBC patients (20.0 vs. 10.6%, p < 0.001). Among MBC patients, chemotherapy (HR 0.69, 95% CI 0.53-0.89, p = 0.004) and radiotherapy (HR 0.52, 95% CI 0.39-0.69, p < 0.001) were associated with improved survival, while ALND was associated with decreased survival (HR 1.37, 95% CI 1.06-1.77, p = 0.02).

CONCLUSIONS

MBC patients had worse survival than non-MBC patients, independent of receptor status, suggesting that MBC may confer an additional survival disadvantage. Multimodal therapy was associated with improved outcomes, but ALND was not and may be overutilized in MBC.

Metaplastic Carcinoma of the Breast Is More Aggressive Than Triple-negative Breast Cancer: A Study From a Single Institution and Review of Literature

BACKGROUND

We aimed to describe our experience with metaplastic breast carcinoma (MBC), evaluate its clinical outcome compared with triple-negative breast cancer (TNBC), and provide a through and comprehensive review of the literature to date.

MATERIALS AND METHODS

We reviewed MBC cases (n = 46) from our institution. The following variables were recorded: tumor histologic subtype, Nottingham grade, tumor size, lymph node status, Tumor, Node, Metastases stage, biomarkers profile, patient's age and race, therapy modality (chemotherapy and radiation), and survival (disease-free survival [DFS] and overall survival [OS]). The clinical and pathological data for TNBC (n = 508) cases were extracted from the breast cancer database. To compare the survival between MBC and TNBC, a subgroup of MBC cases (n = 40) were matched with TNBC cases (n = 40) on the basis of known prognostic confounders.

RESULTS

There were 17 of 46 (37%) cases with mesenchymal differentiation, 12 (26.1%) squamous cell carcinoma, 14 (30.4%) spindle cell carcinoma, and 3 (6.5%) mixed type. MBC presented at a more advanced stage than TNBC (P = .014) and was more likely to recur (34% vs. 15.5%; P = .004). More MBC patients died from disease than TNBC (29% vs. 16%; P = .05). In the multivariate analysis, MBC had approximately twice the risk of local recurrence than TNBC (95% confidence interval, 1.01-3.83; P = .05). MBC patients had worse DFS and OS than the matched TNBC patients (P < .001 and P = .033, respectively). A review of the literature comparing MBC versus TNBC is presented.

CONCLUSION

Our results suggest that MBC is clinically more aggressive than TNBC. Further studies might help delineate the differences between these 2 entities.

Metaplastic Breast Cancer: Molecular Typing and Identification of Potential Targeted Therapies at a Single Institution

INTRODUCTION

Metaplastic breast carcinoma (MBC) is a rare and aggressive histologic subtype of breast cancer comprising approximately 0.5% to 5.0% of all invasive breast cancers with a poor prognosis and limited therapeutic options.

PATIENTS AND METHODS

We investigated MBC at our institution to evaluate outcomes and investigate the molecular profile of our cohort to determine the presence of mutations for which there are targeted therapies.

RESULTS

We found our cohort to consist mainly of the matrix-producing variant (72%) with 48% having the stereotypical estrogen receptor-negative/progesterone receptor-negative/human epidermal growth factor receptor-2-negative phenotype. While the overall survival of our cohort was an average of 1679 days (4.6 years), we had a surprising number of patients with second primaries (40%) and distant metastases (40%), yet few recurrences (12%). Molecular analysis of the tumors indicated that one gene mutation, CSFIR, was significantly associated with outcome (P = .021); however, the cohort was defined by frequent mutations in ERBB4 (36%), PIK3CA (48%), and FLT3 (60%), for which there are now targeted therapies.

CONCLUSION

While surgery is the appropriate first step in the management of this aggressive malignancy, the collection of data pertaining to the use of targeted agents, although anecdotal, may provide clues to better treatment for these patients.

Management and Outcomes in Metaplastic Breast Cancer

Metaplastic breast cancer (MBC) constitutes a rare clinical entity with special clinicopathologic, immunohistochemical, and molecular features. Resistance to systemic therapies, whether chemotherapy or hormonal therapy, is among its main characteristics, which in turn explains the poor prognosis and renders its management a challenge. Thus, the scope of the present review is to discuss the current therapeutic strategies for MBC in clinical practice and the corresponding outcomes and to suggest possible directions for future research. Potential novel targeted therapies could provide a hope for better outcomes but limited data are available owing to the rarity of MBC. As knowledge accumulates on the pathogenesis and genetic characteristics of MBC, emphasis should be given to the implementation of more targeted treatments, which will allow more efficient and individualized management of the disease.