Case study shows how accurate diagnosis can guide personalized treatment for renal oncocytoma

A new case report was published in Volume 17 of Oncotarget on July 2, 2026, titled "Renal oncocytoma: Α case report and literature review."

The study was led by first and corresponding author Areti Kalfoutzou from the Second Propaedeutic Department of Internal Medicine, Attikon General Hospital, National and Kapodistrian University of Athens, Greece.

Renal oncocytoma is a rare benign tumor of the kidney that accounts for approximately 5–9% of renal epithelial tumors. Although it is considered benign, it often resembles kidney cancer on imaging studies, making accurate diagnosis challenging. Because treatment strategies differ substantially between benign oncocytoma and malignant renal tumors, establishing the correct diagnosis is essential to avoid unnecessary surgery while ensuring appropriate patient care.

In this report, the researchers describe the case of an 82-year-old woman who presented with two months of gross hematuria. Contrast-enhanced computed tomography (CT) identified a 55 × 34 mm exophytic lesion arising from the upper pole of the left kidney. Based on its imaging characteristics, the mass was initially classified as a Bosniak category IV renal lesion, raising strong suspicion for renal malignancy.

Instead of proceeding directly to surgery, the clinical team performed a CT-guided percutaneous biopsy. Histopathological examination, supported by immunohistochemical analysis, established the diagnosis of renal oncocytoma. The tumor showed positive staining for E-cadherin and cyclin D1, focal positivity for cytokeratin 7 (CK7), and negative staining for CD117, carbonic anhydrase IX (CAIX), vimentin, and RCC, findings that supported the final diagnosis.

Following multidisciplinary discussion, the tumor board recommended percutaneous cryoablation because of the lesion's relatively small size and indolent nature. This minimally invasive approach was particularly appropriate given the patient's clinical circumstances. More than two years after treatment, annual imaging has demonstrated no evidence of disease progression.

The authors also review the broader diagnostic challenges associated with renal oncocytoma. Conventional CT and magnetic resonance imaging can localize these tumors but often cannot reliably distinguish them from chromophobe renal cell carcinoma or other renal neoplasms. Histopathological evaluation remains the diagnostic gold standard, while percutaneous biopsy is increasingly recognized as a safe and minimally invasive method for establishing the diagnosis before treatment decisions are made.

The report also discusses advances in pathological diagnosis. Immunohistochemical markers such as CK7 and cyclin D1, together with characteristic histological features, can help differentiate renal oncocytoma from chromophobe renal cell carcinoma and hybrid oncocytic/chromophobe tumors, improving diagnostic confidence in challenging cases.

"This case supports the strategy of individualized treatment for renal oncocytoma, balancing tumor characteristics, patient comorbidities, and potential treatment risks to achieve optimal outcomes."

According to the authors, management decisions should be individualized, taking into account tumor size, patient age, symptoms, and overall health status. For selected elderly patients or those at higher surgical risk, minimally invasive approaches such as percutaneous cryoablation may provide effective disease control while preserving kidney function and reducing treatment-related morbidity.

Overall, this case highlights the importance of combining imaging, biopsy, histopathology, immunohistochemistry, and multidisciplinary evaluation when managing renal masses. The findings demonstrate how accurate diagnosis can guide personalized treatment decisions, helping some patients avoid unnecessary surgery while achieving excellent clinical outcomes.