Mesenchymal Hamartoma of the Liver and DICER1 Syndrome

Abstract

Mesenchymal hamartoma of the liver (MHL) is a benign tumor affecting children that is characterized by a primitive myxoid stroma with cystically dilated bile ducts. Alterations involving chromosome 19q13 are a recurrent underlying cause of MHL; these alterations activate the chromosome 19 microRNA cluster (C19MC). Other cases remain unexplained. We describe two children with MHLs that harbored germline <i>DICER1</i> pathogenic variants. Analysis of tumor tissue from one of the children revealed two <i>DICER1</i> "hits." Mutations in <i>DICER1</i> dysregulate microRNAs, mimicking the effect of the activation of C19MC. Our data suggest that MHL is a new phenotype of DICER1 syndrome. (Funded by the Canadian Institutes of Health Research and others.).