p120 is a proliferation-associated nucleolar protein found in most human malignant tumors, but not in resting normal cells. The expression of p120 has been statistically correlated with the proliferation capacity in human lung cancer cells and could be a prognostic marker for resected Stage I lung adenocarcinoma. In colorectal cancer the altered localization of p120 catenin has been found to correspond with loss of cytoplasmic localization of E-cadherin and has been associated with a significant reduction in patient survival time and an increase in tumor stage and lymph node metastasis. This data highlights the importance of both p120 catenin and E-cadherin in the progression of colorectal carcinoma. The distinction between lobular and ductal lesions of the breast is important in several circumstances. Diagnostic reproducibility of lobular vs. ductal lesions, based on histology alone, is less than optimal. The proper distinction between atypical lobular hyperplasia, lobular carcinoma in situ and lowgrade ductal carcinoma in situ is critical for patient management. E-cadherin, a negative membrane marker for lobular neoplasia, is useful in the distinction of ductal neoplasia vs. lobular; however as a negative marker for lobular carcinoma, it can be difficult to interpret, particularly in challenging cases. Studies have shown accurate categorization of ductal vs. lobular neoplasia in the breast was achieved p120 staining and helped give further clarification in the separation of low-grade ductal carcinoma in situ from lobular neoplasia. Diagnostically, p120 can be particularly useful in identifying early lesions of lobular neoplasia. Studies have also shown that altered expression of p120 catenin predicts poor outcome in invasive breast cancer.