Association between molecular subtypes and lymph node status in invasive breast cancer.

BACKGROUND The predictors for the involvement of lymph node (LN) have been widely studied. But the implication of the molecular type has not been well studied. Using the database of our institution, we investigated this relation. METHODS Patients with T1 and T2 primary breast cancer without distant metastasis were included in our study from 2012 Jan to 2013 Dec. All patients undertook the resection of the primary and the axillary lymph nodes (ALNs). We collected the clinical data including age at diagnosis, the status of ER, PR and HER2, tumor size, nodal status, and histological type. The relationship between demographic, tumor characteristics and lymph node status was evaluated. RESULTS 814 patients were included in our study. The number and the percentage (in parentheses) of each type of breast cancer is as follows: Luminal A 230 (28.3%), Luminal Her2- 284 (34.9%), Luminal Her2+ 104 (12.8%), HER2+ 72 (8.8%), TNBC 124 (15.2%). On univariate and multivariate analysis, tumor size and tumor subtype show statistical significance with LN involvement. Using TNBC as a reference, both Luminal B type (Luminal HER2-, Luminal HER2+) shows significant higher probability of LN involvement. CONCLUSIONS LN involvement is an intrinsic characteristic for molecular subtype of breast cancer. Triple positive and triple negative breast cancer accounts the most and least possibility of LN involvement.