To study the clinicopathological and genomic characteristics of Xp11.2 translocation renal cell carcinoma (Xp11.2 RCC) in adults, we analyzed 9 Xp11.2 RCCs, confirmed by transcription factor E3 (TFE3) immunohistochemistry, in patients aged >= 20 years. TFE3 expression was also determined in 12 cases of alveolar soft part sarcoma (ASPS) served as a positive control. Comparative genomic hybridization (CGH) was used to investigate genomic imbalances in all Xp11.2 RCC cases. Most of our Xp11.2 RCC patients (5/9) presented with TNM stages 3-4, and 6 patients died 10 months to 7 years after their operation. Histologically, Xp11.2 RCC was composed of a mixed papillary nested/alveolar growth pattern (8/9). Immunostaining showed that all Xp11.2 RCC and ASPS cases had strong TFE3 expression and high positive ratios for p53 and vimentin. However, there were significant differences in the expression of AMACR (p<0.001), AE1/AE3 (p=0.002), and CD10 (p=0.024) between the 2 diseases. CGH profiles showed chromosomal imbalances in all 9 Xp11.2 RCC cases; gains were observed in chromosomes Xp11 (6/9), 7q20-25, 12q25-31 (5/9), 7p16-24 (4/9), 8p12-13, 8q20-21, 16q20-22, 17q25-26, 20q22-23 (4/9), and losses occurred frequently on chromosomes 3p12-16, 9q31-32, 14q22-24 (4/9). Our Conclusions show Xp11.2 RCC that occur in adults may be aggressive cancers, the expressions of AMACR, CD10, AE1/AE3 are helpful in the differential diagnosis between Xp11.2 RCC and ASPS, and CGH assay is a useful complementary method for confirming the diagnosis of Xp11.2 RCC.