BACKGROUND

Metaplastic breast cancer is a rare histologic variant among breast cancers. We sought to investigate the impact of hormone receptor status in metaplastic breast cancer and compare outcomes with common histologic variants of breast cancer.

METHODS

The study was performed utilizing the Surveillance, Epidemiology, and End Results database. A query was made for patients with metaplastic breast cancer from 2000 to 2010. A separate query identified all patients with infiltrating ductal (IDC) or lobular (ILC) carcinoma during the same period. Effect of hormone receptor status was evaluated using Cox regression analysis. Significance was assessed for p < 0.05.

RESULTS

A total of 2,338 patients with metaplastic breast cancer were available for study. Most tumors were hormone receptor negative (79.0 %) and greater than or equal to grade 3 (82.9 %). For comparison, 382,667 and 44,813 patients with IDC and ILC, respectively, were obtained. Overall 5-year survival for metaplastic breast cancer was 62.2 % compared with 81.2 % for IDC (p < 0.001) and 80.2 % for ILC (p < 0.001). For metaplastic cases, no difference in 5-year survival was found between hormone-positive and hormone-negative tumors (65.7 vs. 63.5 %; p = 0.70). Multivariate analysis demonstrated metaplastic histology as an independent risk factor for cancer-related mortality both among hormone-positive (hazard ratio [HR] 2.4; 95 % confidence interval [CI] 1.8-3.0; p < 0.001) and hormone-negative (HR 1.7; 95 % CI 1.5-1.9; p < 0.001) breast cancers.

CONCLUSION

Metaplastic breast cancer is an aggressive histologic variant that portends a poor prognosis compared with common breast cancer subtypes. Contrary to other breast cancers, hormone receptor positivity does not improve prognosis in metaplastic breast cancer.