Renal oncocytoma overview

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Homa Najafi, M.D.[2] Shanshan Cen, M.D. [3]

Overview

Renal oncocytoma is a relatively rare and benign tumor. On gross pathology, tan or mahogany brown, well circumscribed tumor, and central scar are characteristic findings of renal oncocytoma. On microscopic histopathological analysis, oncocytes and large eosinophilic cells are characteristic findings of renal oncocytoma. Renal oncocytoma must be differentiated from renal cell carcinoma, metanephric neoplasms, and renal leiomyoma. The incidence of renal oncocytoma increases with age; the median age at diagnosis is 55 years. The male to female ratio is approximately 2 to 1. Symptoms of renal oncocytoma include hematuria and flank pain. Abdonimal CT scan, ultrasound, and intravenous pyelogram may be helpful in the diagnosis of renal oncocytoma. Surgery is the mainstay of treatment for renal oncocytoma. Prognosis is generally excellent.

Historical perspective

Renal oncocytoma was first discovered by Zippel, in 1942 and Klein and Valensi were the first to demonstrate the pathologic characteristics of renal oncocytoma as “proximal tubular adenoma with oncocytic features” in 1976.

Classification

There is no established system for the classification of renal oncocytoma.

Pathophysiology

On gross pathology, tan or mahogany brown, well circumscribed tumor, and central scar are characteristic findings of renal oncocytoma. On microscopic histopathological analysis, oncocytes and large eosinophilic cells are characteristic findings of renal oncocytoma.

Causes

There are no established causes for renal oncocytoma.

Differential Diagnosis

Renal oncocytoma must be differentiated from other diseases that cause abdominal mass, abdominal pain and hematuria such as wilms tumor, renal cell carcinoma, rhabdoid kidney disease, polycystic kidney disease, and other urogenital mass.

Epidemiology and Demographics

The incidence of renal oncocytoma is approximately 3% to 7% of solid renal resected tumors. Patients of all age groups may develop renal oncocytoma. The age of patients can be differ from 10 to 94 years. The incidence of renal oncocytoma increases with age; the median age at the time of surgery is 62 to 68 years. Males are more commonly affected by renal oncocytoma than females. The male to female ratio is approximately 2 to 1.

Risk Fctors

There are no established risk factors for renal oncocytoma.

Screening

There is insufficient evidence to recommend routine screening for renal oncocytoma.

Prognosis

The median age at the time of surgery is 62 to 68 years. In 10% to 32% of patients with renal oncocytoma, coexcitente RCC are seen. Prognosis is generally excellent, There are only two cases of metastatic renal oncocytoma were reported. Since the definite diagnosis is maintain just after surgery, most of patients are undergone operation.

Diagnosis

History and Symptoms

The majority of patients with renal oncocytoma are asymptomatic. Symptoms are seen in almost only 17% to 21% of patients with renal oncocytoma. Symptoms of renal oncocytoma include hematuria, flank pain, abdominal or flank mass and weight loss.

Physical Examination

Physical examination of patients with renal oncocytoma is usually normal. An abdominal or flank mass may be palpayed during physical examination.

Laboratory Findings

Some patients with renal oncocytoma may have hematuria, in their urine analysis.

X Ray

X-ray is rarely done for the diagnosis of renal oncocytoma.

CT Scan

Abdominal CT scan may be helpful in the diagnosis of renal oncocytoma. Findings on CT scan suggestive ofrenal oncocytoma include solid renal lesion, centralscar (stellate scar), hypervascularity, hypodenseity ( most of the time), and homogenous enhancements.

MRI

Renal MRI may be helpful in the diagnosis of renal oncocytoma. Findings on MRI suggestive of renal oncocytoma include central scar, satellite pattern, pseudo-capsule, hypointensity in T1 and hyperintensity in T2 weighted images. Although, none of these characteristics can differentiate between renal oncocytoma and RCC.

Ultrasound

Renal ultrasound in renal oncocytoma patients may show: solid mass ( help to distinguish solid from cystic mass), central scarring, calcification, central necrosis which none of them characteristics for indicating a specific renal lesion.

Other Imaging Findings

Renal angiography may be helpful in the diagnosis of renal oncocytoma. The “spoke-wheeled” appearance, lucent rim sign, homogeneous capillary flush in the nephrogram phase, lack of wild neoplastic vessels,and both hypovascular or hypervascular may seen on angiography of patients with renal oncocytoma. Although, none of them are specific for renal oncocytoma and they also may seen in RCCs.

Other Diagnostic Studies

Renal mass biopsy may be helpful in the diagnosis of renal oncocytoma. However, distinguishing between oncocytoma and RCC by biopsy is difficult. Since this method only reserved for patients who are at high risk for an operation like very elderly or extremely sick patients. Some complications may happen during renal mass biopsy which are perirenal hemorrhage, pneumothorax ( during biopsy of upper pole tumors) and tumor seeding.

Treatment

Medical Therapy

The mainstay of therapy for renal oncocytoma is surgery.

Surgery

Surgery is the mainstay of treatment for renal oncocytoma.

Primary Prevention

There are no established measures for the primary prevention of renal oncocytoma.

Secondary Prevention

There are no established measures for the secondary prevention of renal oncocytoma.