Sporadic cases of a particular group of renal cancers associated with a translocation involving Xp11.2, known as the TFE3 transcription factor gene, have been reported in the last 20 years. The group was also classified in 2004 WHO kidney carcinoma classifications. A 79-year-old male patient was investigated at the outpatient department for gross intermittent hematuria. Sonography showed a spherical left kidney with increased total size, without evidence of the corticomedullary differentiation due to parenchymal dyshomogeneity with a neoplasm aspect. CT confirmed the sonographic left kidney findings and showed gross node involvement. Angiography did not show any pathological arterial circulation, but massive thrombotic involvement of the renal vein was evident. Radical nephrectomy with thrombectomy and staging lymphectomy were performed. At pathological examination the kidney parenchyma was completely substituted by white firm tissue. Microscopically the tumor was composed of papillary structures lined by epithelial cells with a clear cytoplasm. Multiple node metastases were found. Immunohistochemical examination showed negativity for epithelial markers (cytokeratin and epithelial membrane antigen) and reactivity for CD10 and TFE3. The genetic and histological aspects of this rare tumor are reported. In addition, we describe clinical, radiological and surgical findings.

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