Malignant Ectomesenchymoma: Series Analysis of a Histologically and Genetically Heterogeneous Tumor

Aims. Malignant ectomesenchymomais a rare pediatric neoplasm with dual mesenchymaland neuroectodermalelements. Mesenchymalcomponent is usually rhabdomyosarcoma, particularly embryonal subtype, whereas neuroectodermalderivatives are frequently a neuroblastictumor. Ectomesenchymomamanifests in various sites given the wide migration of neural crestcells during development, though the pelvis/ perineumis most often involved. Moreover, no unique unifying molecular abnormality has been determined. Methods. We conducted a retrospective study to analyze the spectrum of ectomesenchymaltumors encountered in our pediatric population. Six patients were identified and data pertaining to patients’ demographic, tumor size and site, histologic components with immunophenotypicprofile, molecular alterations, treatment, and outcome were collected. Results. Mesenchymalelements, represented by rhabdomyosarcomain all instances, were the dominant component in the majority of cases (5/6). Embryonal and alveolar morpho...