Introduction: To explore the prognosis and risk stratification of adult microphthalmia-associated transcription factor (MiT) family translocation renal cell carcinoma (mitRCC) to assist clinical strategy. Methods: FISH was used to screen mitRCC patients. The percentage of FISH positive cells was calculated. Papillary and clear cell renal cell carcinoma cases were matched with mitRCC to compare survivals. Non-parametric tests were used to compare differences. X-tile software was used to calculate the optimal cut-off values. Univariable and multivariable survival analyses were performed by COX. Define the high, middle, and low risk groups according to the prognostic factors to analyze the survivals of different groups. Results: A total of 107 mitRCC cases were enrolled including 89 patients of localized or locally advanced mitRCC at diagnosis, accounting for 1.4%. Thirteen patients occurred metastasis postoperatively. Eighteen patients were synchronous metastatic mitRCC. TFE3 accounted for 83.2% (89/107) and TFEB16.8% (18/107). The median follow-up was 42.3 months, and the 5-year Cancer-specific survival (CSS) was 71.4%. Of localized or locally advanced patients, 5-year CSS was 89.1% which was similar to clear-cell renal cell carcinoma (94.4%, p=0.07), but worse than papillary renal cell carcinoma (95.0%, p=0.04). T3~T4, N1, and percentage of FISH positive cells =45% were independent prognostic factors associated with Disease-free survival (DFS). Patients in high-risk group (3 factors; 5-year DFS 0.0%) and median-risk group (2 factors; 37.5%) had worse prognoses than low-risk group (0 to 1 factors; 96.6%) (p < 0.01). The 3-year Overall survival (OS) was 37.9%, which was worse than clear-cell renal cell carcinoma (61.4%) and papillary renal cell carcinoma (46.7%) (p < 0.01). The percentage of FISH positive cells, initial metastatic organ number, initial symptom, and paraneoplastic syndrome were independent prognostic factors. Patients in high-risk group (3 to 4 factors; 3-year OS 0.0%) and median-risk group (2 factors; 20.0%) had worse prognoses than low-risk group (0 to 1 factors; 100.0%) (p < 0.01). Conclusions: Localized or locally advanced patients preferred surgeries and the prognosis was good, but patients with 2 to 3 risk factors of pathological T3~T4, N1, percentage of FISH positive cells >45% were more likely to develop postoperative metastases. Metastatic patients had poorer prognoses than papillary renal cell carcinoma and clear-cell renal cell carcinoma, especially in patients with 2 or more risk factors. SOURCE OF Funding: None
