RCC may present with an abdominal mass, abdominal pain, or hematuria. In a series of 41 children with RCC, the median age was 124 months with 46% presenting with localized stage I and stage II disease, 29% with stage III disease, and 22% with stage IV disease using the Robson classification system. The sites of metastases were the lungs, liver, and lymph nodes. EFS and OS were each about 55% at 20 years posttreatment. Patients with stage I and stage II disease had an 89% OS rate, while those with stage III and stage IV disease had a 23% OS rate at 20 years posttreatment. An important difference between the outcomes in children and adults with RCC is the prognostic significance of local lymph node involvement. Adults presenting with RCC and involved lymph nodes have a 5-year OS of approximately 20%, but the literature suggests that 72% of children with RCC and local lymph node involvement at diagnosis (without distant metastases) survive their disease. In another series of 49 patients from a population-based cancer registry, the findings were essentially confirmed. In this series, 33% of the patients had papillary subtype, 22% had translocation type, 16% were unclassified, and 6% had clear-cell subtype. Survival at 5 years was 96% for patients with localized disease, 75% for patients with positive regional lymph nodes, and 33% for patients with distant metastatic RCC.
Some nephrogenic rests may become hyperplastic which may produce a thick rind of blastemal or tubular cells that enlarge the kidney. The diagnosis may be made radiographically, most readily by magnetic resonance imaging, in which the homogeneity of the hypointense rind-like lesion on contrast-enhanced imaging differentiates it from Wilms tumor. Biopsy often cannot discriminate Wilms tumor from these hyperplastic nephrogenic rests. Differentiation may occur following the administration of chemotherapy. Current recommendations are for treatment with vincristine and dactinomycin until nearly complete resolution as determined by imaging. Even with treatment (vincristine and dactinomycin), about half of children diagnosed with nephroblastomatosis will develop Wilms tumor within 36 months. In a series of 52 patients, three patients died of recurrent Wilms tumor. In treated children, as many as one-third of Wilms tumors are anaplastic, probably as a result of selection of chemotherapy-resistant tumors, so early detection is critical. Patients are followed by imaging at a maximum interval of 3 months for a minimum of 7 years. Given the high incidence of bilaterality and the subsequent Wilms tumors, renal-sparing surgery is indicated. These patients will be eligible for treatment on the COG-AREN0534 trial with vincristine and dactinomycin.
Neuroepithelial Tumors of the Kidney
Neuroepithelial tumors of the kidney (NETK) are extremely rare and demonstrate a unique proclivity for young adults. It is a highly aggressive neoplasm, more often presenting with penetration of the renal capsule, extension into the renal vein, and metastases.[60,61] Primary NETK consist of primitive neuroectodermal tumors characterized by CD99 (MIC-2) positivity and the detection of EWS/FLI-1 fusion transcripts. Within NETK, focal, atypical histologic features have been seen including clear cell sarcoma, RT, malignant peripheral nerve sheath tumors, and paraganglioma.[60,62] (Refer to the PDQ summary on Ewing Sarcoma Family of Tumors for more information about neuroepithelial tumors.)