Cell-cell adhesion plays a critical role in the establishment and maintenance of cell polarity and cell society. Reduced cell-cell adhesiveness allows cancer cells to disobey the social order, resulting in destruction of the histological structure, the morphological hallmark of malignant tumors. Morbidity in most cancer patients is not due to primary cancer but to metastatic disease. Thus, understanding the progression of tumors to metastatic state and the changes that take place in highly aggressive cells is important in the development of novel approaches to the diagnosis and treatment of progressive malignancies. Cell adhesion molecules are implicated in human carcinogenesis. E-cadherin is a calcium-dependent cell adhesion molecule the intact function of which is crucial for the establishment and maintenance of epithelial tissue polarity and structural integrity. The gene encoding E-cadherin (CDH1, on chromosome 16q22.1) was one of the first to be considered as an invasion-suppressor gene. Mutations in CDH1 occur in diffuse type gastric cancer, lobular breast cancer, and endometrial cancer. In human cancers, partial or complete loss of E-cadherin expression correlates with malignancy. Through immunohistochemical analysis it has been assessed the abnormal expressions of E-cadherin in three types of cancer: gastric carcinoma, lobular breast carcinomas and cutaneous melanoma and the correlation with the multistep process of metastasis.