Cancer breast represents the second leading cause of cancer deaths in females. It constitutes 33% of all female cancers in Egyptian National Cancer Institute. The prognosis is very good if detected at an early stage. Intraductal proliferative lesions are associated with an increased risk of subsequent development of invasive carcinoma. Cyclin D1 nuclear protein has a checkpoint function; it can promote cell proliferation or induce growth arrest and apoptosis. This study compared the expression of cyclin D1 protein immunohistochemically in both fibrocystic changes of the female breast with or without ductal proliferation and invasive duct carcinoma (NOS). It was found that all estimated prognostic histopathological and clinical criteria were not statistically significantly correlated with cyclin D1 staining in both benign and malignant groups.