Eosinophilic vacuolated tumor of the kidney misdiagnosed as upper tract urothelial carcinoma: a case report and literature review.

Background: Eosinophilic vacuolated tumor (EVT) is a rare renal tumor subtype recognized in the 2022 WHO Classification of Urinary and Male Genital System Tumors under the category of other oncocytic renal tumors, though it has not yet been formally established as an independent diagnostic entity. Due to the lack of typical clinical and imaging features, preoperative diagnosis remains challenging. This article reports a case of EVT misdiagnosed as upper tract urothelial carcinoma (UTUC), aiming to improve clinical awareness of the atypical presentations of this tumor. Case summary: A 71-year-old male patient presented with painless gross hematuria for one week. He had a history of long-term smoking and renal calculi. CT revealed a soft tissue mass in the right renal pelvis region with marked enhancement during the corticomedullary phase and filling defect of the renal pelvis during the excretory phase. PET-CT showed a hypermetabolic nodule in the renal hilum region. Urine cytology revealed clusters of cells with nuclear atypia. Based on these findings, a preoperative diagnosis of UTUC was made, and laparoscopic right radical nephroureterectomy with bladder cuff excision was performed. Based on histological morphology and immunophenotype, the pathological diagnosis was eosinophilic vacuolated tumor (EVT). At 9-month follow-up, renal function remained unaffected, with no evidence of tumor recurrence or metastasis. Conclusion: EVT involving the renal sinus may present as a renal pelvis mass, which can be clinically misdiagnosed as UTUC. For renal pelvis tumors with atypical imaging features, preoperative biopsy should be actively pursued to establish a definitive pathological diagnosis and avoid overextension of surgical scope.