Mruthyunjayappa S, et al. - The researchers intended to investigate the incidence of bilateral breast cancer (BBC, reportedly ranges from 1.4 to 11.8%) in the era of modern medicine and evaluate the clinicopathologic features and prognostic outcomes in comparison with unilateral BC (UBC). One hundred and ten patients out of 5,941 patients with stage I-III BC diagnosed between 1998 and 2013, developed BBC, including 58 synchronous BBC (SBBC, the interval between the first and the contralateral BC ≤ 3 months) and 52 metachronous BBC (MBBC, interval > 3 months). Among patients with MBBC, the median time to the second tumor was 67.9 months. BBC had a correlation with a significantly lower rate of having a ductal type, high grade, HER2-positive or node-positive disease when compared with UBC, however, for age, race, ER/PR status, or pathologic tumor stage, no variation was observed. SBBC was strongly related to a lobular phenotype, non-high grade, and ER/PR-positive disease and further exhibited a significantly greater concordant rate for ER, PR, and HER2 status when contrasted with MBBC. in comparison with those with UBC, patients with BBC had a markedly worse distant relapse-free survival (RFS) but a comparable disease-specific survival (DSS). Being African American, having a high histologic grade and higher pathologic tumor or node stage were significantly correlated with a worse prognosis, whereas, SBBC had a correlation with a favorable RFS by multivariate analysis. For DSS in patients with BBC, nodal status was the only independent predictor. therefore, in this unique subset of patients, more research into the complex biologic and clinical behavior of BBC may provide unique insights into the therapeutic strategies in the pursuit of precision medicine.