Tissue Handling for Genome-Wide Expression Analysis A Review of the Issues, Evidence, and Opportunities

Abstract Context.—Molecular diagnostic applications that use microarrays to analyze large numbers of genes simultaneously require high-quality mRNA. As these genome-wide expression assays become more commonly used in medical practice, pathologists and oncologists will benefit from understanding the importance of obtaining high-quality RNA in order to generate reliable diagnostic and prognostic information, especially as these relate to cancer. Objective.—To review the effects that different tissue preservation techniques have on RNA quality and to provide practical advice on changes in tissue acquisition and handling that may soon be needed for certain clinical situations. Data Sources.—A review of recent literature on RNA quality, tissue fixation, cancer diagnosis, and gene expression analysis. Conclusions.—Studies have consistently shown that frozen tissue yields more intact RNA than formalin-fixed, paraffin-embedded tissue. The chemical modification, cross-linking, and fragmentation caused by formalin ...