Risk stratification by hormonal receptor (ER, PgR) and HER2 status in small (≤1cm) invasive breast cancer: Who might be a possible candidate for adjuvant treatment?

564 Background: With the increasing use of screening mammography, the proportion of ≤ 1 cm invasive breast cancer is increasing. Identification of breast cancer molecular subtypes has resulted in a better appreciation of the biologic heterogeneity, which is not fully explained by clinicopathologic features including staging system. The aims of this study were: 1) to identify the risk factors of systemic metastases in patients with ≤ 1 cm invasive breast cancer and 2) to investigate the patients group at greatest risk of such failure even in these small tumors. Method: Data were collected retrospectively in the breast cancer registry of our institution for patients with invasive breast cancer from October 1994 to December 2004. Results: Of 4,036 patients who received curative breast cancer surgery, 466 patients who had T1a or T1b breast cancer were identified. 39 patients who received neoadjuvant chemotherapy were excluded in this study. Ipsilateral axillary lymph node involvement was found in 13% (57/427)...