Neuroectodermal elements are part of the morphological spectrum of DICER1-associated neoplasms

Many sarcomas with DICER1 pathogenic variants (PVs) exhibit a characteristic morphology, including a subepithelial layer of malignant mesenchymal cells, areas of rhabdomyoblastic differentiation and cartilaginous and/or osseous elements. We report 5 DICER1-associated neoplasms (1 moderately to poorly differentiated Sertoli Leydig cell tumour and 4 sarcomas) containing variable amounts of neuroectodermal elements. The neoplasms predominantly involved or were in close proximity to the female genital tract (ovary, uterine corpus, abdominal and pelvic cavity) and occurred in females aged 14 months to 54 years. The neuroectodermal elements were characterised by solid and tubular/rosette-like patterns and variable immunoreactivity with SALL4 and neuroendocrine markers. In some cases, the neuroectodermal component was focal while in others it was exclusive. In one case, the focal neuroectodermal component within an ovarian Sertoli Leydig cell tumour resulted in extraovarian metastasis. In reporting these cases, we suggest that neuroectodermal elements, including pure neuroectodermal tumours, are part of the morphological spectrum of DICER1-associated neoplasms. It is important that pathologists recognize that a neuroectodermal component (often admixed with other elements) may be a feature of such neoplasms. This will facilitate appropriate tumour and/or germline testing which could lead to the identification of germline DICER1 PVs (DICER1 syndrome). Three of the patients we report were subsequently shown to have a germline DICER1 PV.