This study investigated the factors causing the distinct properties of TNBC and non-TNBC, and PRR15 was identified as a DEG between TNBC and non-TNBC with substantially decreased expression in TNBC than normal samples, while high levels were found in the overall breast cancer or non-TNBC compared with their counterparts, which was confirmed by several perspectives. The gene discussed is PRR15; the disease is breast cancer.