PRCC-TFE3 renal cell carcinoma in a boy with a history of contralateral mesoblastic nephroma

The genetics of renal tumors in children is widely recognized. However, most of the studies published to date emphasize the association between Wilms tumor and the WT-1 gene. Recently, a unique translocation between the X chromosome and chromosome 1 or t(X;1) has been described in several reports of renal cell carcinomas (RCCs) diagnosed in children and adolescents that results in PRCC-TFE3 gene fusion. We report here a 9-year old African-American boy with a history of a right congenital mesoblastic nephroma treated with nephrectomy and followed by annual checkups. After 9 years, he was diagnosed with a mass at the hilum of the left kidney during the work-up of new-onset hypertension. A limited biopsy revealed densely hyalinized connective tissue that was initially interpreted to be a hyalinized contralateral mesoblastic nephroma. The child received chemotherapy, but the mass continued to grow. He underwent a left nephrectomy, and the pathology was diagnostic for a clear cell RCC. Chromosomal analysis disclosed a t(X;1)(p11.2;q21) translocation, which is known to result in a PRCC-TFE3 gene fusion. The tumor showed nuclear labeling for TFE3 protein by immunohistochemistry, supporting the above diagnosis. He has been on hemodialysis, is tumor free, and has not been receiving chemotherapy for 24 months. This is the first report of a RCC as a second malignant neoplasm in a child treated for a congenital mesoblastic nephroma.