Background: Triple-negative (TN) breast cancers lack estrogen receptor (ER), progesterone receptor (PR), and HER2/neu amplification (HER2). Few studies have been dedicated to characterizing this subset of cancer. Materials and Methods: Retrospective review of a prospectively collected database of patients treated for invasive breast cancer at a single institution. Three tumor marker groups were compared: TN [ER-/PR-/HER2-], HER2+ [ERx/PRx/HER2+], and ER+ [ER+/PRx/HER2-]. Results: Over 8 years, 123 TN, 210 HER2+, and 728 ER+ patients were identified. On average, TN patients were younger (mean age TN 59.7, HER2+ 62.0, ER+ 64.5 years, P = 0.0001). They were referred for genetic testing more frequently (17% TN, 10% HER2+, 10% ER+, P = 0.055) and were most likely to have a BRCA mutation identified if tested (24% TN, 10% HER2+, 4% ER+, P = 0.019). TN tumors were larger (mean size 2.1 cm TN, 2.0 cm HER2+, 1.8 cm ER+, P = 0.031) and most commonly detected by breast exam (54% TN, 43% HER2+, 42% ER+, P = 0.025). Lymph node involvement was least common with TN tumors (21% TN, 37% HER2+, 32% ER+, P = 0.013), and angiolymphatic invasion was less common for TN than HER2+ (18% TN, 24% HER2+, 15% ER+, P = 0.006). TN patients had significantly higher local or regional recurrence (5.7% TN, 2.9% HER2+, 1.0% ER+, P = 0.001), and the worst 5-year overall survival, although this did not reach statistical significance (85% ± 6% TN, 94% ± 2% HER2+, 91% ± 2% ER+). Conclusions: TN breast cancers are associated with unique patient presentations, tumor characteristics, and clinical outcomes of which clinicians and investigators should be aware.
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