A 13-year-old female with Xp11.2 translocation renal cell carcinoma; the first case diagnosed at Siriraj Hospital.

Xp11.2 translocation renal cell carcinomas are rare tumors characterized by translocations involving chromosome Xp11.2. These tumors are predominantly reported in pediatric patients. The authors report Xp11.2 translocation renal cell carcinoma in a 13-year-old girl who presented with asymptomatic palpable right renal mass. Right radical nephrectomy was performed and revealed a well-defined solid mass at the lower pole of the kidney. Microscopically, the tumor was composed of sheets and nests of clear to pale eosinophilic cells with some alveolar growth pattern. Psammoma bodies were detected. Immunohistochemically, the tumor cells marked with TFE3, focally marked with smooth muscle actin, HMB-45, CD68, progesterone receptor (PR) and CD10 but did not mark with epithelial markers (AE1/AE3, EMA and CAM5.2), vimentin, S-100 and p53. The presence of psammoma bodies is an important diagnostic clue for these tumors. Cytogenetic study and/or immunohistochemistry for TFE3 protein are needed for confirming the diagnosis. Currently, surgery seems to be the most effective therapy Pediatric patients with these tumors are believed to have a favorable prognosis.