Notable Histologic Findings in a "Normal" Cohort: The National Institutes of Health Genotype-Tissue Expression (GTEx) Project.

Context.—: The National Institutes of Health (NIH) Genotype-Tissue Expression (GTEx) project was designed to evaluate how genetic variation and epigenetic effects influence gene expression in normal tissue.

Objective.—: To ensure that the grossly normal-appearing tissues collected were free from disease, each specimen underwent histologic evaluation.

Design.—: In total, nearly 30 000 tissue aliquots collected from almost 1000 postmortem donors underwent histologic review by project pathologists, and detailed observations of any abnormalities or lesions present were recorded.

Results.—: Despite sampling of normal-appearing tissue, in-depth review revealed incidental findings among GTEx samples that included neoplastic, autoimmune, and genetic conditions; the incidence of some of these conditions among GTEx donors differed from those previously reported for other populations. A number of age-related abnormalities observed during histologic review of tissue specimens are also described.

Conclusions.—: Histologic findings from the GTEx project may serve to improve populational awareness of several conditions and present a unique opportunity for others to explore age- and gender-influenced conditions. Resources from the study, including histologic image and sequencing data, are publicly available for research.