In this chapter provides an in-depth exploration of breast cancer and malignant breast diseases, covering their diagnosis, histopathology, imaging, and treatment. It begins with Atypical Breast Hyperplasia, followed by detailed discussions of Ductal Carcinoma (in situ and invasive) and Lobular Carcinoma, addressing each subtype’s pathology and management. The chapter also reviews rarer malignancies such as Metastatic Breast Disease, Lymphoma, and Inflammatory Breast Cancer, highlighting their distinct clinical features and treatments. A structured approach integrates pathophysiology, imaging evaluations, and treatment protocols, concluding with key insights to aid in the comprehensive management of malignant breast diseases.