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

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.

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.

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.

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.