Twisted Tapestry of Tumors: Updates in Molecular Pathology of Breast Tumors.

This article explores the expanding role of molecular diagnostics in breast pathology. It emphasizes how immunohistochemistry, fluorescence in situ hybridization, and next-generation sequencing define tumor subtypes with recurrent genetic alterations, while predictive biomarkers such as ESR1, human epidermal growth factor receptor 2, PD-L1, and BRCA1/2 direct targeted therapies. The article highlights the diagnostic value of entity-specific fusions and mutations, the therapeutic implications of rare molecular events, and the promise of artificial intelligence-driven gene expression-based prediction models in cancers of unknown primary. These advances illustrate how molecular tools complement morphology, refine classification, and enable precision medicine in breast cancer care.