Lessons from 801 clinical TFE3/TFEB fluorescence in situ hybridization assays performed on renal cell carcinoma suspicious for MiTF family aberrations

Objectives Fluorescence in situ hybridization (FISH) assays for the detection of chromosomal rearrangements involving TFE3 and TFEB are considered the gold standard for the diagnosis of MiTF family altered renal cell carcinoma (MiTF-RCC). We reviewed 801 clinical TFE3/TFEB FISH assays performed at our tertiary-level institution between 2014 and 2023 on kidney tumors suspicious at the morphologic or biomarker level for MiTF aberrations. Methods We summarized and analyzed clinical information, TFE3/TFEB FISH results, and available biomarker staining results in a cohort of 453 consecutive kidney tumor cases suspicious for MiTF-RCC. Results In total, 61 of 434 (14%) kidney tumors were confirmed for TFE3 translocation; 10 of 367 cases (2.7%) were confirmed for TFEB translocation. Since TFEB amplification interpretation was implemented in our service line, 20 of 306 cases (6.5%) were diagnosed with TFEB amplification. Importantly, TFE3 and TFEB rearrangements were never co-detected within the same kidney tumor. Patients with TFEB amplification were significantly older (P < .001) than patients with TFE3 or TFEB translocation. Kidney tumors with TFEB amplification were seen to be at least 3 times as common as those with TFEB translocation. Conclusions Clinical TFE3/TFEB FISH assays successfully identified and confirmed rare MiTF-RCC with TFE3 and TFEB rearrangements. Although morphologic and biomarker features associated with a kidney tumor may be suggestive of MiTF-RCC, clinical TFE3/TFEB FISH assays are crucial for a confirmation and definitive subclassification of patients with MiTF-RCC.