Xp11.2 translocation renal cell carcinomas (TRCCs) are rare tumors recently accepted as a separated tumor type in 2004 WHO classification. To diagnose these tumors, histological recognition and confirmation of translocation are necessary. While the incidence of overall renal cell carcinomas (RCCs) is increased after the age of 40, Xp11.2 TRCCs are predominantly reported in young patients. The incidence of these tumors in Thailand has not been evaluated.To identify the frequency of Xp11.2 TRCCs, clinical presentation and follow-up information in 40 year-old or younger patients by using TFE3 immunostaining to confirm the translocation.All cases of 0- to 40-years-old patients diagnosed as RCCs from nephrectomy specimens between 2001 and 2011 at Siriraj Hospital were reviewed by one pathology resident and two pathologists. Immunohistochemical staining for TFE3 was performed on cases morphologically suspected for TRCC or showing unusual histology.Four cases consistent with Xp11.2 TRCC were identified by TFE3 immunostaining from all 31 cases (12.9%). Three cases were females and one was male. Two cases were at stage 4 and passed away several months after the operation. The other two patients were at stage 2. One patient is alive without recurrence for at least 36 months after surgery alone. The other died from underlying SLE.TFE3 immunostaining is a useful andpractical toolfor screening and diagnosis of Xp11.2 TRCCs, but staining results can be difficult to interpret. Thus, genetic analysis is still necessary especially when immunostaining shows problematic result. Fresh tumor tissue sampling in all young patients is recommended in case of further genetic studies needed.