Metaplastic breast carcinoma: clinicopathologic features and prognostic value of triple negativity

Metaplastic breast carcinomas (MBC) are a rare type of breast cancer and are generally characterized by hormone receptor and human epidermal growth factor receptor 2 (HER2) negativity. There is a paucity of information on prognosis according to hormone receptor and HER2 expression for these rare tumors. The aim of this study was to compare the clinical features and prognosis between triple-negative metaplastic carcinoma (TNMC) and non-triple-negative metaplastic carcinoma (NTNMC).

We retrospectively analyzed MBC patients treated at Seoul National University Hospital between 1996 and 2006. The medical records were reviewed.

Fifty-one patients were identified. At a median follow-up of 40.8 months, the 3-year disease-free survival (DFS) and overall survival (OS) rates were 75.5% and 86.3%, respectively. Non-triple negativity (P = 0.012) correlated significantly with OS in multivariate analysis. Of the 51 patients, 41 (80.4%) had TNMC and 10 (19.6%) had NTNMC. The two groups did not differ significantly by age, tumor size or nodal status. In patients with NTNMC, the positivity rates for estrogen receptor, progesterone receptor and HER2 were 20.0%, 30.0% and 80.0% in NTNMC. The 3-year OS rates in patients with TNMC and NTNMC were 93.4% and 58.2%, respectively (P = 0.007). With respect to DFS, there was no statistically significant difference between patients with TNMC and those with NTNMC (P = 0.149).

In MBC, the non-triple-negative group had a poor prognosis compared with the triple-negative group, which is contrary to what has been reported in patients with invasive ductal carcinoma of breast. Further research exploring the mechanism underlying this result is needed.