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.