Imaging of synchronous multifocal renal masses: a case report.

Background: Synchronous multifocal renal masses (SMRMs) are defined as the coexistence of two or more histologically distinct tumors within the same kidney. Such combinations are rare and frequently mimic multifocal renal cell carcinoma (RCC) or other malignancies, complicating diagnosis and management. The synchronous occurrence of renal oncocytoma (RO), perivascular epithelioid cell tumor (PEComa), and ganglioneuroma (GN) in a single kidney is exceptionally rare. Case presentation: A 79-year-old woman was admitted with a 1-year history of an incidentally detected right renal mass on ultrasonography. The mass was initially discovered on ultrasonography during a routine health screening; the patient declined further evaluation at that time due to financial constraints and the absence of symptoms. She had no flank pain, gross hematuria, fever, or weight loss. Physical examination revealed right costovertebral angle tenderness on percussion, without palpable masses. Laboratory tests, including renal function and urinalysis, were unremarkable. Renal ultrasonography demonstrated a heterogeneous hypoechoic mass in the upper-mid pole and a slightly hyperechoic mass in the lower pole of the right kidney; both showed internal strip-like and peripheral annular blood flow on color Doppler. CT urography revealed three right-sided lesions with distinct imaging characteristics involving the upper pole, renal hilum, and lower pole. Chest CT was performed for staging and showed no evidence of pulmonary metastasis. Laparoscopic radical right nephrectomy was performed after multidisciplinary discussion. Histopathology confirmed RO in the upper pole, PEComa in the lower pole, and GN at the renal hilum, supported by immunohistochemical staining. The patient was counseled regarding the potential for a hereditary syndrome given the multifocal nature of her tumors; formal genetic testing was recommended but the patient declined. The postoperative course was uneventful. At 1-month follow-up, ultrasonography showed no recurrence and compensatory hypertrophy of the contralateral kidney, with preserved renal function. Conclusion: This case highlights a unique combination of three benign tumors of distinct lineages within a single kidney. Although histopathology remains the gold standard, cross-sectional imaging is critical for characterizing SMRMs and differentiating them from multifocal malignancy. Genetic counseling should be considered in patients presenting with multifocal renal tumors of diverse histology.