Abstract Introduction: Triple negative breast cancer (TNBC), defined as estrogen, progesterone, and HER2/Neu receptor-negative is biologically more aggressive than non-TNBC. Whether TNBC presents at a more advanced local/regional stage is controversial. We sought to determine whether TNBC had more frequent lymph node positivity. Methods: ER and PR status was determined by routine immunohistochemical analysis. HER2/Neu status was determined by immunohistochemistry; if 2+ equivocal status was noted, fluorescence in situ hybridization was performed for confirmation. Patients with a clinically negative axilla underwent sentinel lymph node biopsy, and if the sentinel node was positive, underwent immediate completion axillary node dissection. Lymph node positivity was determined by hematoxlyn-eosin staining. The main outcome measures were lymph node status and pathologic tumor size. Statistical differences were compared by means of paired t-test and chi-squared test where appropriate. Results: Between January 1, 2004 and December 31, 2010, 501 women with invasive breast cancer were treated at our institution. These patients ranged in age from 25 to 93 years (mean 57.6 yr), with 53.1% of patients self-reported as non-Hispanic white and 43.7% non-Hispanic black. TNBC patients were younger (mean 55.0 yr vs. 58.3 yr, p = 0.005), and were more often non-Hispanic black (52.7% vs. 41.1%, p = 0.03). The mean pathological tumor size of the entire population was 1.86 cm (range 0 to 18 cm). One hundred twelve patients (22.4%) were TNBC. The mean pathological tumor size for TNBC compared to non-TNBC patients was 2.07 cm (range 0 to 8.7 cm) and 1.80 cm (range 0 to 18 cm) (p = 0.068). There was a statistically significant difference in the T-stage at presentation between TNBC and non-TNBC tumors (T1, 58.9% TNBC vs. 72.0% non-TNBC; T2, 34.8% TNBC vs. 22.4% non-TNBC; T3/T4, 6.3% TNBC vs. 5.6% non-TNBC, p = 0.02). One hundred sixty patients (31.9%) were node positive. The number of positive lymph nodes in the TNBC patients ranged from 1–18, and the non-TNBC ranged from 1–35 (TNBC mean 2.94 vs. non-TNBC mean 3.94, p = 0.09). TNBC patients were more often node positive than non-TNBC (39.3% vs. 29.3%, p < 0.05). However, when stratified by T-stage, the differences did not achieve statistical significance (T1, 31.8% TNBC vs. 21.8% non-TNBC, p = 0.11; T2, 51.3% vs. 46.0%, p = 0.70; T3/T4, 57.1% vs. 59.1%, p = 1.0), despite a trend toward greater node positivity in earlier T-stage TNBC tumors. Conclusions: TNBC is more frequently lymph node positive than non-TNBC. This is largely attributable to more node positivity in early T-stage tumors. These data provide further evidence for the poor prognosis of TNBC and the increased likelihood of nodal metastases in early T-stage tumors. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-01-17.