Renal cell carcinomas associated with Xp11.2 translocations ( TFE3 gene fusions) are rare tumors predominantly reported in children. We studied 5 cases of translocation carcinoma in adult patients, 18 years or older (mean age, 32.6 years). Tumors were examined histologically, immunohistochemically, and electron microscopically and correlated with the clinical picture. Most tumors showed solid sheets of clear to eosinophilic cells with rich vasculature and foci of papillary or pseudopapillary architecture. All cases showed strong nuclear positivity for TFE3. Vimentin and CD10 were positive in the cytoplasm. A panel of cytokeratin antibodies, smooth muscle actin, CD45, HMB45, and calretinin were negative. Patients had nonspecific initial complaints and were diagnosed with advanced disease, most with distant metastases. Various treatments met with minimal success. Unlike pediatric patients, the adult patients followed a rapidly terminal course, with a mean survival of 18 months after diagnosis (range, 10-24 months).