TFE3-renal carcinoma in an adult patient: a case with strong expression of phosphorylated hepatocyte growth factor (HGFR)/Met.

TFE3-renal carcinoma is rare in adults. Patients with this disease often have a poor prognosis, because it has reached an advanced stage at presentation, and there is lack of an effective therapy. The exact mechanism of its malignant behavior is still unclear. In recent years, a significant relationship between TFE3 fusion protein and hepatocyte growth factor receptor (HGFR)/Met tyrosine kinase activity was reported in several malignancies. We previously reported that phosphorylation of HGFR/Met was associated with malignant aggressiveness and survival in patients with conventional RCC. Here, using immunohistochemical techniques, we examined two types of phosphorylated HGFR/Met (pY1234/1235 and pY1349) in a specimen of a 29-year-old man with TFE3-renal carcinoma. Strong expression of both proteins was detected in carcinoma cells, but not in normal kidney tissues. In addition, they were expressed more strongly in TFE3-renal carcinoma than in conventional RCC. Although tumor was diagnosed at T1N0M0 and the patient received radical nephrectomy, the tumor metastasized to multiple organs, and he died 2 years after surgery. We speculate that upregulated phosphorylation of HGFR/Met could be partly associated with the malignant aggressiveness and poor survival of this patient.