Clinicopathological features and prognosis of MED15-TFE3 rearrangement renal cell carcinoma: An updated report.

492 Background: TFE3-rearranged renal cell carcinoma (rRCC) is uncommon, and demonstrates unique heterogenous morphological features and distinct immune characteristics. MED15-TFE3 is a rare gene fusion that usually present as an extensive cystic mass with low malignant potential and is more susceptible to immune check point inhibitor. Identifying the clinical characteristics is crucial for the treatment. Methods: All samples were collected retrospectively from West China Hospital between 8/2011 and 5/2024. Diagnosis of MED15-TFE3 gene fusion was confirmed by RNA sequencing and fluorescence in situ hybridization. Both clinicopathological features and follow-up prognosis information were collected for further analysis. Results: The detailed information of 16 cases were described in the table. The median age was 47.5 years (range, 22 to 70 years). Majority of the cases were female (12/16). All patientes were surgically treated (radical nephrecomy: 8; partial nephrectomy: 7; cytoreductive surgery: 1). At initial diagnosis, most cases (14/16) were localized disease, while two patients had positive regional lymph nodes metastasis, and one patient had distant metastasis. For the patients without distant metastasis (n=15), two patients developed metastasis with disease-free survival of 11.4 and 29.0 months, respectively. As for the pathological features, 14 (87.5%) of the casess presented cystic morphologically, and other two (12.5%) were papillary. Except for one patient with diatant metastasis at initial diagnosis, all patients (15/16) were in G2 by ISUP score. For metastatic patients, 3 received first-line therapy (1 axitinib, 1 axitinib + sintilimab, 1 sunitinib), 2 received second-line therapy (1 axitinib + sintilimab, 1 axitinib + toripalimab), 1 received third-line therapy (axitinib + toripalimab and combined with everolimus). They are still under follow-up. Conclusions: MED15-TFE3rRCC mainly present low-grade cystic renal neoplasm with favorable prognosis. For metastatic MED15-TFE3 rRCC, there is no standard therapy currently. Clinicopathological characteristics and prognosis of 16 MED15-TFE3 rRCC cases. Characteristics Cases Age, median (range), years 47.5 (22, 70) Gender Male 4 Female 12 Morphology Cystic 2 Papillary 14 Tumor size, median (range), cm 5.6 (3.3, 14.0) Nephrectomy Radical 8 Partial 7 Cytoreductive 1 T stage T1 10 T2 3 T3 3 N stage N0 14 N1 2 M stage M0 15 M1 1 ISUP grade 2 15 3 1 Distant metastasis Synchronous 2 Metachronous 2 No 12 Survival status Alive 15 Dead <jats: