Malignant primitive neuroepithelial tumour of soft tissues mimicking a cellular ependymoma

A malignant small blue-cell soft tissue tumour in a 13 year-old girl is reported. By light microscopy the tumour showed prominent pseudo-rosettes suggesting peripheral neuroepithelial tumour (PNET) with ependymal differentiation or extraspinal cellular ependymoma. Ultrastructural and immunocytochemical findings helped in excluding an ependymal neoplasm (low-grade malignancy) and supported the diagnosis of malignant primitive PNET mimicking a cellular ependymoma (high-grade malignancy).