CHD1 (chromodomain helicase DNA protein binding domain 1) gene controls the transcriptional activity across the genome. It is recurrently deleted in 10%-25% of primary and metastatic prostate cancer, and particularly focal homozygous deletions are restricted to ETS-negative tumors. CHD1 deletion may contribute to the distinctive patterns of genomic instability observed in CHD1del tumors.The SPOP-mutant/CHD1-deleted subset of prostate cancer have characteristic molecular features, including high levels of DNA methylation, homogeneous gene expression patterns, distinct somatic copy-number alterations (SCNA), as well as frequent overexpression of SPINK1 mRNA.