Sample processing considerations for detecting copy number changes in formalin-fixed, paraffin-embedded tissues.

The Whole Genome Sampling Analysis (WGSA) assay in combination with Affymetrix GeneChip Mapping Arrays is used for copy number analysis of high-quality DNA samples (i.e., samples that have been collected from blood, fresh or frozen tissue, or cell lines). Formalin-fixed, paraffin-embedded (FFPE) samples, however, represent the most prevalent form of archived clinical samples, but they provide additional challenges for molecular assays. FFPE processing usually results in the degradation of FFPE DNA and in the contamination and chemical modification of these DNA samples. Because of these issues, FFPE DNA is not suitable for all molecular assays designed for high-quality DNA samples. Strategies recommended for processing FFPE DNA samples through WGSA and to the Mapping arrays are described here.