Diverse fusion patterns and heterogeneous clinicopathologic features of renal cell carcinoma with t(6;11)...

Renal cell carcinoma (RCC) with t(6;11) translocation, involving the transcription factor EB (TFEB) and Alpha, also known as MALATI, (TFEB RCC), is extremely rare, with only 20 cases reported to date. It may be frequently misdiagnosed because of a lack of established characteristics. TFEB RCCs are predominantly seen in younger patients and are generally indolent, with only 2 cases of metastasis. Genetic analysis has been limited, showing break points upstream of TFEB exon 3, yielding only a single transcript. We examined 3 new adult Japanese TFEB RCC cases by means of precise clinicopathologic, immunohistochemical, cytogenetic, and molecular analyses and compared them with 200 ordinary RCCs. A 57-year-old man was the oldest patient with TFEB RCC at the time of this study. Although the tumor had histology typical of translocation RCC, its fusion points were different between the genomic and transcript coordinates. A 37-year-old man had an aggressive course resulting in death. The tumor had 2 variants of messenger ribonucleic acid. A 47-year-old man showed borderline histologic and immunohistochemical features between TFEB RCC and chromophobe-type RCC. The tumor had a fusion point in TFEB exon 4, downstream of the wild-type ATG in exon 3. Nuclear expression of the TFEB protein was detected, and a Western blotting analysis identified a protein similar in size to the wild-type TFEB protein. Immunohistochemistry is useful for the diagnosis of these tumors, and TFEB RCCs have heterogeneous clinicopathologic features and more diverse fusion patterns than previously thought, requiring attention to polymerase chain reaction experiments for diagnosis. Our study will contribute to the correct diagnosis of TFEB RCC.