The frequency of PIK3CA mutation and amplification was various and their clinical significances have not been clarified in Korean patients with invasive breast carcinoma (IBC). The study aimed to investigate the clinical and prognostic significances of PIK3CA mutation and amplification in IBC patients. DNA was isolated from paired normal and tumoral tissues in 128 IBC patients and the mutation and expression of PIK3CA gene were analyzed. PIK3CA mutation and expression was detected in 14.3% and 21.9% of IBC patients, respectively. And the level of PIK3CA expression was not different according to the presence of PIK3CA mutation (p = 0.775). PIK3CA mutation and expression were significantly associated with Luminal A type (p = 0.017 and p = 0.011, respectively). However, they did not have any clinical and prognostic values for IBC patients. This result suggested that alterations of PIK3CA pathway contribute to the pathogenesis of specific type of IBC.