The Incidence of Oncocytoma and Angiomyolipoma in Patients Undergoing Nephron-Sparing Surgery for Small Renal Masses

Background: Oncocytoma and angiomyolipoma (AML) are benign renal tumors that may mimic malignant lesions on imaging. With the increasing use of partial nephrectomy (PN) for renal masses, accurate preoperative characterization of these lesions is essential. This study highlights the role of partial nephrectomy as a valuable diagnostic tool in situations where imaging is inconclusive or raises concern for malignancy without definitive confirmation. In the absence of a reliable preoperative diagnosis, partial nephrectomy provides direct histologic verification with minimal perioperative morbidity. Moreover, it offers curative potential when malignancy is present. By achieving both diagnostic certainty and renal preservation, this approach is well-suited for clinical scenarios in which imaging ambiguity might otherwise result in overtreatment through radical surgery or undertreatment Material and methods: in this retrospective study, we reviewed our 5-year experience (2019–2024), 188 partial nephrectomies—including bilateral procedures and operations on solitary kidneys—using robotic and open approaches. All of these 30 tumors were solid renal masses with indeterminate imaging features or suspicious characteristics suggestive of malignancy, further underscoring the limitations of current preoperative diagnostic modalities. Results: Histopathological evaluation confirmed benign renal tumors in 30 cases, with oncocytoma diagnosed in 18 cases (16 robotic, 2 open) and AML in 12 cases (9 robotic, 3 open). Conclusions: Even when imaging raises suspicion of malignancy or remains inconclusive, many small renal masses are ultimately confirmed as benign upon histopathological examination. This study underscores the diagnostic uncertainty associated with small renal tumors and highlights the value of partial nephrectomy as a decisive diagnostic intervention. In situations where non-invasive modalities fail to provide definitive answers, partial nephrectomy offers tissue confirmation with minimal morbidity. Furthermore, when malignancy is present, this approach ensures appropriate oncologic management while preserving renal function. Our findings support the integration of this strategy into routine clinical practice, particularly when diagnostic clarity is essential for guiding safe and effective treatment.