DICER1-associated hepatic cystic neoplasm with pleuropulmonary blastoma-like features: a novel clinicopathologic diagnosis.

This report documents a unique multicystic neoplasm of the liver in an 8-month-old boy with a heterozygous germline pathogenic DICER1 variant. This neoplasm, initially considered most likely a mesenchymal hamartoma based on imaging, demonstrated the characteristic histologic pattern of embryonal rhabdomyosarcoma residing in the subepithelial or cambium layer-like zone of the epithelial-lined cysts. Thus, although the differential diagnosis includes mesenchymal hamartoma, a young child with a multicystic mass lesion in the liver, lung, or kidney should both raise the possibility of a germline pathogenic DICER1 variant and also not be mistaken for one of the other hepatic neoplasms of childhood.