Incidence of axillary lymph node metastases in T1a and T1b breast carcinoma

Background: We investigated the incidence of axillary lymph node metastases in patients with T1a (less than or equal to 0.5 cm) and T1b (>0.5 cm and less than or equal to 1.0 cm) breast cancers. Methods: The charts of 2000 patients who underwent axillary lymph node dissection for breast cancer at our institution from 1989 to 1991 were reviewed. Of these, 81 patients had Tla and 166 had T1b primary breast cancers. Results: Among the 247 patients with T1a and T1b breast cancers, nodal metastases were present in 30 (12.1%), with a 7.4% positivity rate for patients with T1a and 14.5% positivity rate for T1b tumors. Of the 212 patients who had greater than or equal to 10 nodes dissected, 29 (13.7%) had positive nodes. Of those, 6 of 60 (10.0%) patients with T1a and 23 of 152 (15.1%) with T1b tumors had positive nodes. The presence of lymphovascular invasion (LVI) predicted a significantly higher nodal positivity rate (27.8% vs. 10.9%, p = 0.05). Conclusions: Of patients with adequately evaluated axillae, 10% with T1a and 15% with T1b cancers were found to have nodal metastases. Although LVI was significantly associated with a higher risk of lymph node metastases, we could not characterize any subgroup at acceptably low risk of nodal positivity. Until a more useful prognostic indicator is discovered, axillary dissection should continue to be part of the mainstay of management for small breast cancers.