The APC gene encodes a tumor suppressor protein that acts as an antagonist of the Wnt signaling pathway. APC promotes rapid degradation of beta-catenin and participates in Wnt signaling as a negative regulator. APC is also involved in other processes including cell migration, cell adhesion, transcriptional activation and apoptosis. Germline defects in this gene cause familial adenomatous polyposis (FAP), an autosomal dominant pre-malignant disease that usually progresses to malignancy. Somatic mutations in APC have been reported in around 2% of breast carcinomas. One study found that APC mutations in up to 18% of their breast cancer cohort and at a significantly high frequency in advanced stages of primary breast cancers. The APC K1454E variant has not been previously reported in breast carcinoma. The significance of this variant should be interpreted within the clinical context.