Ovarian embryonal rhabdomyosarcoma is a rare manifestation of the DICER1 syndrome

Embryonal rhabdomyosarcoma (ERMS), a malignant soft tissue sarcoma, is one of the most common paediatric cancers. Certain ERMS tumours are associated with the DICER1 syndrome, a distinctive tumour predisposition syndrome caused by germ-line mutations in the microRNA-maturation pathway gene, DICER1. In addition to germ-line DICER1 mutations, highly characteristic somatic mutations have been identified in several DICER1-associated tumour types. These so-called \"hotspot\" mutations affect highly conserved amino acid residues central to the catalytic activity of the DICER1 ribonuclease IIIb domain.\n\nPrimary ovarian ERMS (oERMS) is extremely rare. We present a case of a 6-year-old girl with an oERMS found to harbour two mutations in DICER1. In addition to the oERMS, the girl also exhibited other DICER1 phenotypes, including cystic nephroma (CN) and multinodular goitre. Somatic investigations of the CN revealed the presence of a hotspot DICER1 mutation different from that in the oERMS. Of particular interest is the CN presented at the age of 12 years, which is much older than previously reported age range of susceptibility (birth to four years of age).\n\nThis report documents both germ-line and highly characteristic somatic DICER1 mutations in a case of oERMS, adding to the expanding spectrum of rare childhood tumours in the DICER1 syndrome.