Metaplastic Breast Carcinoma: Clinicopathological Characteristics, Treatment Patterns, and Outcomes

Background: Metaplastic breast carcinoma (MBC) is a rare and aggressive subtype of breast cancer, accounting for less than 1% of all cases. MBC is characterized by a metaplastic transformation of glandular epithelium into squamous and/or mesenchymal elements. Most tumors are triple-negative, lacking expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), which limits targeted therapeutic options. MBC also exhibits marked histopathological heterogeneity and high chemoresistance. Methods: We conducted a retrospective study of 15 patients with histopathologically confirmed MBC treated at a tertiary care center in India. All cases demonstrated a triple-negative immunophenotype (ER < 1%, PR < 1%, HER2-negative), with documented metaplastic differentiation. Detailed data on demographics, clinicopathological features, treatment, and outcomes were collected and analyzed. Results: The median age at diagnosis was 52 years. All patients presented with advanced disease: stage II in 60% (n = 9) and stage III in 40% (n = 6). Metaplastic differentiation included spindle cell features in 40% (n = 6), squamous features in 33.3% (n = 5), and mixed patterns in 26.7% (n = 4). Tumors were more commonly located in the right breast (73.3%, n = 11). Surgical management included mastectomy in 60% (n = 9) and breast-conserving surgery in 26.7% (n = 4). Neoadjuvant chemotherapy (NAC) was administered to six patients (40%), achieving a pathological complete response (pCR) in two of these (33.3%). Adjuvant chemotherapy was given to seven patients (46.7%), and 11 patients (73.3%) received radiotherapy. At the last follow-up, six (40%) were alive and disease-free, two (13.3%) were alive with disease, three (20%) had died, two (13.3%) were lost to follow-up, and two (13.3%) had incomplete assessment. Conclusions: MBC in this cohort presented with aggressive histopathological features and predominantly advanced-stage disease. These findings highlight the need for improved breast cancer awareness, early detection, and individualized treatment strategies, particularly in resource-limited settings.