DICER1‐mutated rhabdomyosarcoma of the ovary with teratoid features

Abstract

DICER1‐mutated rhabdomyosarcoma is a rare, emerging entity with a predilection for the gynecologic and genitourinary tracts. We report here a case of DICER1‐mutated rhabdomyosarcoma of the ovary in a 14 years old girl which displayed interspersed mature teratoid glands, neuroectodermal rosettes and immature blastematous‐like tubes. Morphologically the sarcomatous component predominated, corresponding to a high grade spindle cell rhabdomyosarcoma with botryoid features. Islets of cartilage were present. The sarcomatous proliferation encased the teratoid glands, forming cambium layer‐like arrangements. The sarcoma cells were Myogenin and MYOD1 positive, the neuroectodermal rosettes expressed SALL4 along with cytokeratins and EMA and were negative for Inhibin; immature blastematous‐like tubes were negative for SALL4 and Inhibin. Whole RNA‐ and targeted DNA‐sequencing revealed two DICER1 mutations in exon 26: c.5113G>A: p.(Glu1705Lys) and exon 12: c.1642C>T: p.(Gln548X). The sarcomatous component harbored a complex genetic profile while the teratoid component was diploid, none of the above displayed abnormality of 12p. DICER1‐mutated sarcomas display pathological features similar to embryonal rhabdomyosarcomas, botryoid type. They also display heterogeneous features combining cartilage foci, teratoid mature glands, immature blastematous‐like tubes and/or neuroectodermal components. Molecular testing remains necessary to confirm the diagnosis. Further studies need to clarify the nosology of DICER1‐mutated sarcomas and devise specific therapeutic strategies.