A new case report published in Volume 17 of Oncotarget on July 2, 2026, describes the diagnosis and management of a rare benign kidney tumor known as renal oncocytoma. The study was led by Areti Kalfoutzou from the Second Propaedeutic Department of Internal Medicine at Attikon General Hospital, National and Kapodistrian University of Athens, Greece.
Renal oncocytoma accounts for approximately 5–9% of renal epithelial tumors. Although considered benign, these tumors often resemble malignant kidney cancers on imaging studies, making accurate diagnosis challenging. Treatment strategies differ substantially between benign oncocytoma and malignant renal tumors, so establishing the correct diagnosis is essential to avoid unnecessary surgery while ensuring appropriate patient care.
The case involved an 82-year-old woman who presented with two months of gross hematuria. Imaging identified a mass in her left kidney that was initially classified as Bosniak category IV—a designation raising strong suspicion for malignancy. Instead of proceeding directly to surgery, clinicians performed a CT-guided percutaneous biopsy. Histopathological examination and immunohistochemical analysis confirmed the diagnosis of renal oncocytoma, with specific staining patterns supporting this finding.
Following multidisciplinary discussion, the tumor board recommended percutaneous cryoablation due to the lesion's size and indolent nature. This minimally invasive approach was considered appropriate given the patient's clinical circumstances. More than two years after treatment, annual imaging has shown no evidence of disease progression.
The authors review broader diagnostic challenges associated with renal oncocytoma: conventional CT and MRI can localize these tumors but often cannot reliably distinguish them from chromophobe renal cell carcinoma or other neoplasms. Histopathological evaluation remains the gold standard for diagnosis; percutaneous biopsy is increasingly recognized as a safe method for establishing diagnosis before making treatment decisions.
"This case supports the strategy of individualized treatment for renal oncocytoma, balancing tumor characteristics, patient comorbidities, and potential treatment risks to achieve optimal outcomes," the authors say. Management decisions should be tailored based on tumor size, patient age and health status—minimally invasive options like cryoablation may be effective for selected elderly patients or those at higher surgical risk.
