Primary malignant neuroepithelial tumors of the kidney - A clinicopathologic analysis of 146 adult and pediatric cases from the National Wilms' TumorStudy Group Pathology Center

Primary malignant neuroepithelial tumors of the kidney (NETKs) comprise a g roup of primitive, highly malignant neoplasms that histologically and clini cally are not well characterized. A large cohort of 146 of these tumors, oc curring in adults and children, has been collected at a single depository s ite, the National Wilms' Tumor Study Group (NWTSG) Pathology Center. The au thors undertook a systematic retrospective review of the histologic, ultras tructural, and clinical features of these tumors, based on materials collec ted by the NWTSG and the consultation files of one of the authors (J.B.B.). Histologic features were generally those of primitive neural tumors with v arying amounts of rosettes and neuropil; however, a large proportion of cas es displayed unusual features such as spindle cells, ganglion cells, clear cell sarcoma-like foci, rhabdoid cells, epithelioid cells, and organoid foc i. CD99 staining had been performed on 69 cases and showed membranous stain ing in 65. The NETKs were present in patients with a wide age spectrum, ran ging from 1 month to 71 years (median, 18 years). EWS/FLII fusion analysis using reverse transcriptase-polymerase chain reaction and immunohistochemic al stains for cytokeratin, chromogranin, and epithelial membrane antigen we re performed successfully on a subset of 45 cases with available paraffin b locks. Only 13 of the 45 were fusion-positive, and there was no correlation between fusion status and histology, presence of rosettes, ultrastructural features, or cytokeratin positivity. CD99-negative cases: were usually fus ion-negative (six of seven cases), and all three chromogranin-positive case s were fusion-negative. Tumor staging, performed on 72 clearly defined and quantifiable cases by using NWTSG criteria, indicated that these are aggres sive tumors. because only six were Stage 1, compared with 16 Stage 2, 31 St age 3, and 19 Stage 1 lesions. The authors conclude that NETKs are a somewh at diverse group of generally aggressive, high-grade lesions that may prese nt in a wide age range and are difficult to characterize without immunohist ochemistry and cytogenetics/molecular biology.