Abstract
Metaplastic breast carcinoma (MpBC) is a rare special histologic subtype of breast carcinoma characterized by the presence of squamous and/or mesenchymal differentiation. Most MpBCs are of triple-negative phenotype and neoadjuvant chemotherapy (NAC) is frequently utilized in patients with MpBC. The aim of this study was to evaluate response to NAC in a retrospective cohort of MpBCs. We identified 44 patients with MpBC treated with NAC at our center between 2002 and 2018. Median age was 48 years, 86% were clinical stage II–III, and 36% were clinically node-positive. Most (80%) MpBCs were triple-negative or low (1–10%) hormonal receptor positive and HER2 negative on pre-NAC biopsy. While on NAC, 49% showed no clinical response or clinico-radiological progression. Matrix-producing subtype was associated with clinico-radiological response (p = 0.0036). Post NAC, two patients initially ineligible for breast-conserving surgery (BCS) were downstaged to be eligible for BCS, whereas three patients potentially eligible for BCS before treatment became ineligible due to disease progression. Only one (2%) patient had a pathologic complete response (pCR). Among the 16 patients presenting with biopsy-proven clinical node-positive disease, 3 (19%) had nodal pCR. Axillary lymph node dissection was avoided in 3 (19%) patients who had successful axillary downstaging. Residual cancer burden (RCB) was assessed in 22 patients and was significantly associated with disease-free survival and overall survival. We observed a poor response or even disease progression on NAC among patients with MpBC, suggesting that NAC should be reserved for patients with inoperable MpBC.
Highlights
Metaplastic breast carcinoma (MpBC) is a rare special histologic subtype of breast carcinoma, which includes a heterogeneous group of invasive carcinomas characterized by the presence of squamous and/or mesenchymal differentiation[1]
From 2002 to 2018, 44 patients with MpBC treated with neoadjuvant chemotherapy (NAC) were identified in the institutional database
In this study, we observed a poor response to NAC in patients with MpBC, with only one patient achieving pathologic complete response (pCR), 22% of the patients exhibited no clinical and radiological response, and 27% with progression while on NAC, in contrast to the 30–50% pCR rate in triple-negative breast cancer (TNBC) reported in the literature[20,21,22,23]
Summary
Metaplastic breast carcinoma (MpBC) is a rare special histologic subtype of breast carcinoma, which includes a heterogeneous group of invasive carcinomas characterized by the presence of squamous and/or mesenchymal differentiation[1]. Include spindle cell carcinoma, squamous cell carcinoma, and metaplastic carcinoma with mesenchymal differentiation, which includes matrix-producing carcinoma. Low-grade adenosquamous carcinoma and fibromatosis-like metaplastic carcinoma are the rare low-grade variants with a relatively favorable prognosis which differs from the more common high-grade MpBCs2–5. MpBC typically presents as a rapidly growing mass that is often palpable and larger in size compared to invasive carcinoma no special type (NST)[6,7]. Patients with MpBC tend to have worse disease-free survival and overall survival when compared to common forms of triple-negative breast cancer (TNBC)[10,12,13,14,15,16,17,18,19]
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