Clear Cell Melanoma of the Renal Pelvis Presenting as a Primary Tumor

Abstract

TO date only 3 cases of malignant melanoma presenting as a renal pelvic mass have been reported in adulthood.1.2 To our knowledge we report the first primary malignant melanoma composed of clear cells in the renal pelvis of a child. CASE REPORT A 3-year-old girl was found to have microscopic hematuria during a routine medical examination. Excretory urography revealed a filling defect in the left renal pelvis. Abdominal sonography showed a 2 cm. isoechoic tumor with normal renal parenchyma within the lesion. Abdominal computerized tomography confirmed the lesion in the renal pelvis and demonstrated no evidence of visceral metastasis (fig. 1). Left radical nephrectomy was performed for the presumed diagnosis of Wilms tumor. Histological evaluation of the surgical specimen revealed a solid tumor composed of clear cells with focal pigmentation in the renal pelvis. The transitional cell epithelium was intact (fig. 2). Fontana-Masson staining was positive for melanin and tumor cells were immunoreactive for HMB-45. The patient had no history of malignant melanoma and postoperative clinical and radiological evaluation failed to reveal any other focus of melanoma. Microscopic hematuria resolved postoperatively. The patient remained asymptomatic and without evidence of residual disease 13 months after surgery. DISCUSSION