# Microarray expression data

Source: https://onco.cc/terms/microarray-expression/  
OnCo record `microarray-expression` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Microarrays measured gene expression by hybridising labelled RNA to spots of known DNA on a chip; they preceded RNA sequencing and still hold the longest-followed cohorts.

## Summary

A DNA microarray is a collection of microscopic DNA spots on a solid surface used to measure the expression of large numbers of genes at once (Wikipedia). The METABRIC breast cancer cohort of about two thousand patients with long follow-up is microarray based, which makes it the standard external test for TCGA-trained RNA-seq survival models and a stern one: intensities and read counts have different distributions, so a model must be rank- or quantile-normalised to cross platforms.

## Fields

- Kind: Term
- Last checked: 2026-09-24
- Also known as: microarray expression; expression microarray; expression microarrays; microarray data; Affymetrix array; Illumina expression array; hybridisation platform
- Tags: cansim-terms

## Notes

- Listed in the CanSim terms map 1.0.0 (docs/onco/terms.json, generated 2026-09-24), CC BY 4.0, attribution: CanSim project, an open, public-data-first cancer foundation-model programme; CanSim page path /terms/microarray-expression.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/DNA_microarray
- Curtis et al., METABRIC: the genomic and transcriptomic architecture of 2,000 breast tumours (Nature 2012): https://doi.org/10.1038/nature10983
- Wikipedia: https://en.wikipedia.org/wiki/DNA_microarray

## Connected records

- terms: [Batch effects and harmonisation](https://onco.cc/terms/batch-effects/), [Bulk RNA sequencing (RNA-seq) and the full transcriptome](https://onco.cc/terms/bulk-rna-seq/), [Cancer AI vocabulary (CanSim terms map)](https://onco.cc/terms/cancer-ai-vocabulary/), [External validation](https://onco.cc/terms/external-validation/), [Quantile normalisation, rank transforms and z-scores](https://onco.cc/terms/quantile-normalisation/)

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JSON: https://onco.cc/api/v1/entities/microarray-expression.json