Book excerpt: This comprehensive volume reviews current topics and controversies in diagnostic breast pathology, and addresses frequently encountered diagnostic problems using a question and answer format and case presentations. Emphasis is placed on the diagnostic approach as it relates to morphology, clinical and radiographic correlation, differential diagnosis, and ancillary testing including immunohistochemical and molecular analyses. Answers are provided and serve as a practical, evidence-based, and problem solving guide to diagnostic issues having significant impacts on clinical management. Common but diagnostically challenging entities such as papillary lesions and fibroepithelial lesions are discussed in detail, as well as special types of breast cancer including solid papillary carcinoma, lobular lesions and its variants. Uncommon breast lesions such as mesenchymal, lymphoid, and metastatic lesions are also covered. Chapters discuss genetic alterations and molecular abnormalities in breast cancer, and commonly encountered interpretation dilemmas on immunohistochemistry in breast cancer and metastatic cancer to the breast with a focus on prognostic and predictive tumor biomarkers.