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

TNBC is the most aggressive form of BC molecular subtypes. MBC is a rare form of BC that is usually TN. This study compares MBC (n = 46) versus TNBC (508). The study concludes that MBC is more aggressive than TNBC. The study also provides a review of the literature that had similar approach. 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.