Tumor Heterogeneity in Breast Cancer.

Tumor heterogeneity is the topic de jour, partly because molecular biologists and researchers are identifying it using sophisticated gene/DNA analysis techniques. Clinicians and pathologists are well acquainted with marked variability in clinical presentations, tumor histology, and, more importantly, clinical outcomes of their patients. In this review, we address these issues head-on and document that tumor heterogeneity is an old friend (or, more correctly, a foe). We described heterogeneity that exists at all levels—clinical, histologic, and molecular—and briefly outline the strategies that have been used by clinicians and pathologists to tackle this complicated issue.