Renal Cell Carcinoma Associated with Xp11.2 Translocation/TFE3 Gene Fusion: A Case Report with Immunohistochemical and Cytological Features

Abstract

Background: Xp11.2 translocation renal cell carcinoma (RCC) is a rare pediatric neoplasm harboring gene fusions involving TFE3, which plays an important role in cell proliferation and survival. We herein present cytological and histopathological features of RCC associated with Xp11.2 translocation/TFE3 gene fusion. Case Report: A 14-year-old Japanese boy presented at our hospital with complaints of acute abdominal pain (right side), macrohematuria, fever and 10 kg body weight loss. Abdominal CT, MRI and PET-CT scan showed a large mass lesion with calcification in the right kidney, compressing the vena cava inferior and metastasis to the renal hilar lymph nodes. Right radical nephrectomy was performed according to the clinical diagnosis of RCC or Wilms' tumor. A frozen section diagnosis during the operation reported papillary RCC. However, cytology of imprint touch smears from the cut-surface of the tumor led us to suspect Xp11.2 translocation RCC, because epithelial cancer cells showed a positive reaction for TFE3 in the nuclei of neoplastic cells proliferated with a papillary pattern. Histopathology revealed a biphasic population of neoplastic cells, large epithelioid cells with voluminous eosinophilic cytoplasm and severe nuclear atypia and smaller cells with clear cytoplasm and small round nuclei. There were a few psammoma bodies. Immunohistochemistry showed strongly positive nuclear staining of TFE3 protein in the cancer cells. A RT-PCR analysis of an unfixed and fresh tumor sample showed SFPQ/PSF-TFE3 (+). Conclusion: Knowledge of distinctive morphological and immunostaining features of this tumor can help to accurately diagnose this rare subset of translocation associated RCC in routine pathological diagnostic procedures.