β-Catenin is involved in cell adhesion through catenin-cadherin complexes and in the Wnt signaling pathway. Deregulation allows β-Catenin to accumulate in the nucleus, which may be useful in aiding the differential diagnosis of selected neoplasms. β-Catenin adhesion complex impairment is also associated with a poorly differentiated phenotype and increased invasiveness of carcinomas. Cytoplasmic localization of β-Catenin has been demonstrated as a marker of poor outcome in breast cancer patients. Studies suggest it may be useful in the differential diagnosis of selected soft tissue tumors and tumors of the GI tract, pancreas, lung, and female genital tract.