DICER1 syndrome (OMIM#601200) is a familial cancer predisposition syndrome caused by pathogenic germline variants (mutations) in DICER1. This gene encodes DICER1, which is a member of the ribonuclease III family of proteins and is involved in the generation of microRNAs, which modulate gene expression at the posttranscriptional level1. The gene discussed is DICER1; the disease is DICER1-related tumor predisposition.