Background: The incidence of small ( ≤1 cm) node-negative breast cancers (BC) is increasing in mammography-screened populations. These tumors generally have good prognosis with low risk of distant and local recurrence. Methods: A retrospective review of 665 patients classified as having ≤1 cmN0 BC treated in our Institution from 1995 to 2008 was done. Clinical-pathological features and long term outcomes (EFS and OS) were analyzed according to KI67 LI, HER2 status, PR expression and intrinsic sybtypes (luminal A, B, HER2 luminal, HER2, Triple negative-TN). Results: Median age at diagnosis was 60 years (range: 23 to 86 ys).There were 30 T1mic (4.5%), 122 T1a (18.4%) and 513 T1b (77.1%) cancers. A higher proportion of pT1mic+T1a presented poor grading (G3) and had the HER2 and TN subtypes compared with pT1b BC. HER2 was over-expressed or amplificated in 89 (13.4%) of all cases. Chemotherapy with or without hormonal therapy was administered to 18 T1a (12%) and to 82 T1b (16%); hormonal therapy alone in 46 T1a (30%) and 252 T1b (49%). No one received adjuvant trastuzumab. At a 6,5 ys median follow up there were 29 (4.4%) loco-regional (LRR) or distant relapses (DR), 26 (3.9%) controlateral and 21 (31%) other tumors.Similar incidence of LRR, DR and BC related deaths between T1a and T1b was reported. High ki67 (defined as median value = 15%) confirmed its prognostic significance in term of OS, in particular T1b cases (p=0.015), but not in EFS.No difference was found between Luminal B and Luminal A subtypes for any of the outcomes analysed. TN and HER2 subtypes, but not HER2 luminals were correlated with a significantly increased BC related events if compared with the Luminal A subtype (TN 85.7%, HER2 79.4%, Her2 luminal 90.7%, Luminal A 93.7%, Luminal B 89.1%). Conclusions: Our experience confirms good prognosis of ≤ 1 cm N0 BC. However, tumors with more aggressive biological features (high Ki67, HER2 or TN subtypes) had higher incidence of relapses. In this "low stage but adverse biology" BC an intensive (aggressive?) adjuvant approach should always be considered.