Molecular Diagnostics in Breast Cytology

Breast cancer is the most frequent carcinoma in females. It comprises a heterogeneous group of lesions that differ by morphology, clinical presentation, tumor biology, and response to therapy. Traditional classification of breast cancer has been based on evaluation of histologic features, but molecular studies and diagnostic assays have expanded the understanding of tumor biology and are impacting diagnosis, evaluation, and treatment. Here we review the molecular classification of breast cancer, assays commonly used in clinical care, and some tests that show promise in both the early and metastatic setting.