MALIGNANT PERIPHERAL NEUROECTODERMAL TUMORS IN UROLOGY

During the past few years, a new tumor type has emerged in the pediatr ic and adolescent group of cancer patients, which has been designated malignant peripheral neuroectodermal tumor (MPNT). This tumor has some clinical and pathological signs in common with either soft-tissue sar comas or classic Ewing's sarcoma, but is defined as a distinct entity because of its immunohistological characteristics. The tumor expresses neuronal markers, but the pattern varies: chromogranin, neuron-specif ic enolase, synaptophysin, protein S-100 and others. MPNT can occur in the urogenital region. The differential diagnosis on clinical grounds must include Ewing's and soft tissue sarcomas, and also Wilms' tumor and its variants. MPNT are often wide spread in the urogenital region when first diagnosed. Response to radiotherapy and combination chemoth erapy is limited. Radical surgery is not always possible. The prognosi s therefore remains rather poor at this time. A selection of MPNT pati ents is presented to demonstrate the various problems associated with this diagnosis. MRI and CT of all patients showed large tumors with di rect infiltration of the surrounding structures. MRI is the best imagi ng modality for diagnosis and therapy monitoring in these tumors, beca use of its high soft-tissue contrast.