Applying FISH Assay For The Diagnosis Of Xp11.2 Translocation Renal Cell Carcinoma And ASPL-TFE3 Renal Cell Carcinoma

Xp11.2 translocation renal cell carcinoma (RCC) was classified as a new type of RCC in the 2004 World Health Organization classification system and resulted in gene fusion products between transcription factor E3 (TFE3) and the alveolar soft part sarcoma locus (ASPL), along with several other identified genes, including PRCC, PSF, CLTC and NonO. Currently, the diagnosis of Xp11.2 translocation RCC in hospitals relies on pathologic morphology and immunohistochemistry (IHC) evidence, but usually leads to miss diagnosis and misdiagnosis. Furthermore, ASPL-TFE3 RCC is the most common type of Xp11.2 translocation RCC and more malignant than the other subtypes are. The diagnosis of ASPL-TFE3 RCC is always accompanied by lymphatic and distant organ metastasis, and the overall survival is poor. So the accurate diagnosis is the key point in treatment for Xp11.2 translocation RCC and ASPL-TFE3 RCC. Herein, we use a new break-apart FISH probe for diagnosing Xp11.2 translocation RCC and a novel ASPL-TFE3 dual-fusion FISH probe for diagnosing ASPL-TFE3 RCC.Objectives:To improve the accuracy of diagnosis of Xp11.2 translocation RCC and ASPL-TFE3 RCC, we investigated newly designed fluorescence in situ hybridization (FISH) probes and performed them into clinic diagnosis of Xpl 1.2 translocation RCC and ASPL-TFE3 RCC.Methods:(1) Based on the genetic characteristics of Xp11.2 translocation RCC, the TFE3 break-apart FISH probe was designed to test whether the tumor tissues contain the translocation of TFE3 gene depend on the FISH signal. (2) Based on the genetic characteristics of ASPL-TFE3 RCC, the ASPL-TFE3 dual-fusion FISH probe was designed to test whether the tumor tissues contain the ASPL-TFE3 fusion gene. (3) Reverse transcriptase polymerase chain reaction (PCR) was performed on 8 cases for which frozen tissues were available to test the accuracy of FISH assay. (4) The new break-apart TFE3 FISH probe and an ASPL-TFE3 dual-fusion FISH probe were applied to 65 patients with RCC who were less than 45 years old or showed suspicious microscopic features of Xp11.2 translocation RCC in our hospital.Results:(1) We successfully designed and tested the break-apart and ASPL-TFE3 dual-fusion FISH probes in laboratory; (2) Reverse transcriptase PCR confirmed 6 cases of Xp11.2 translocation RCC and 2 cases of ASPL-TFE3 RCC, which showed concordant results with the results of FISH assay in the 8 available frozen cases; (3) Among the 65 cases diagnosed with RCC, twenty-two cases were confirmed as Xp11.2 translocation RCC by break-apart TFE3 FISH, and 6 of these cases were further diagnosed as ASPL-TFE3 RCC by ASPL-TFE3 dual-fusion FISH detection.Conclusions:(1) The break-apart and ASPL-TFE3 dual-fusion FISH assay can accurately detect the translocation of the TFE3 gene and ASPL-TFE3 fusion gene; (2) FISH assays can be used as an adjunctive method to improve the accuracy of diagnosis for Xp11.2 translocation RCC and ASPL-TFE3 RCC.