Tissue microarrays are a platform of condensed histopathology that has revolutionized the translation of basic science to clinical utility. Tissue microarrays have resulted in a paradigm shift from histopathology to immunopathology and moved analysis of small selected samples sets of tens of specimens to a high-throughput environment of hundreds of specimens. Tissue microarrays have influenced validation strategies, but have a role in discovery as well, allowing a pathways approach to analysis of tumors.