DICER1-associated sarcomas at different sites exhibit morphological overlap arguing for a unified nomenclature

Excerpt

In this issue of Virchows, Davidson et al. report an interesting uterine corpus neoplasm, an ectomesenchymoma, in a 72-year old containing a DICER1 mutation [1]. Ectomesenchymoma is an exceedingly rare multiphenotypic sarcoma and in the 5th edition of the World Health Organization (WHO) Classification of Soft Tissue and Bone Tumours, is included in the category of skeletal muscle tumours [2]. It is defined here as exhibiting both mesenchymal and neuroectodermal differentiation and composed of areas resembling rhabdomyosarcoma (prototypically embryonal rhabdomyosarcoma (ERMS)) admixed with variable neuronal/neuroblastic components [2]. The latter covers the entire spectrum of neuroblastic phenotype, ranging from ganglion cells to mature ganglioneuroma, intermediate ganglioneuroblastoma and primitive neuroblastoma [2]. The majority of affected patients are infants or young children (first two decades of life) and most common primary sites include the pelvis, abdomen, retroperitoneum and urogenital organs. The case reported by Davidson et al. exhibited morphological and immunohistochemical evidence of both rhabdomyoblastic and neuroectodermal differentiation and cartilaginous foci were present [1]. Ectomesenchymomas have never been reported to contain DICER1 mutations, although this has not been investigated previously. …