eMedicine Specialties > Radiology > Genitourinary

Oncocytoma, Kidney

Sanjeeva P Kalva, MD, Assistant Radiologist, Massachusetts General Hospital, Instructor in Radiology, Harvard Medical School, Department of Radiology, Massachusetts General Hospital
Dushyant Sahani, MD, Clinical Instructor of Abdominal Radiology and Intervention, Harvard Medical School; Assistant Radiologist, Department of Abdominal Imaging and Intervention, Massachusetts General Hospital

Updated: Dec 29, 2008

Introduction

Contrast-enhanced computed tomography (CT) scan of the abdomen obtained during the nephrographic phase. This CT scan shows a well-defined, enhancing mass lesion in the lower pole of the left kidney. A central hypoattenuating stellate scar is seen.

T1-weighted magnetic resonance image (MRI). This MRI shows a homogeneous, hypointense, well-defined mass in the lower pole of the kidney.

Background

Oncocytoma is the most common benign solid renal tumor.¹ First described by Zippel in 1942,² this tumor represents a distinct pathologic entity. In 1976, Klein and Valensi published their case series of patients with oncocytoma; the authors highlighted the benign course of the disease and its discrete pathologic features.³

Related eMedicine topics:

Renal Cell Carcinoma

Clear Cell Sarcoma of the Kidney

Polycystic Kidney Disease

Cystic Diseases of the Kidney

Acquired Cystic Kidney Disease

Frequency

United States

The incidence of oncocytoma in the US is not clearly known, but this tumor accounts for approximately 3-7% of all renal neoplasms. About 2-12% of oncocytomas are multifocal, and 4-14% are bilateral.⁴

Mortality/Morbidity

• Oncocytomas are benign tumors, and the prognosis after total or partial nephrectomy is excellent.
• Recurrence at the resection site has not been reported.
• A few cases of local invasion and metastases have been reported in the literature, but these probably represent chromophobe RCC, rather than oncocytomas.

Sex

These tumors are more common in males than females, with a rate of 2-3:1, which is similar to that for RCC.

Age

At the time of resection of the tumor, the mean patient age is 62-68 years.

Presentation

Anatomy

The kidneys are retroperitoneal organs that are enclosed in a fibrous capsule and surrounded by perirenal fat. The anterior pararenal fascia separates the kidneys from the pancreas, and the posterior pararenal fascia demarcates the paraspinal muscles from the kidneys. The adrenal glands are located superomedially.

Each kidney is supplied by a main renal artery that arises directly from the aorta. Multiple renal arteries are common, and these play an important role in nephron-sparing surgeries (partial nephrectomy). A single renal vein drains each kidney, and multiple renal veins are uncommon. Lymphatics from the kidney drain into the lymph nodes in the renal hilum, which in turn drain into nodes in the para-aortic region.

On histologic examination, oncocytomas are composed of oncocytes, which are large cells with a granular eosinophilic cytoplasm that, on electron microscopy, show abundant mitochondria. The cells are most commonly arranged in sheets, or they can be arranged in a tubulocystic or combined pattern. The nuclei appear smooth and round, with a minimal degree of nuclear atypia.

The main differential diagnosis on histologic analysis is chromophobe RCC, which also shows granular eosinophilic cytoplasm. However, RCCs have perinuclear clearing. Immunohistochemical tests are also useful to differentiate oncocytoma from chromophobe RCC. Chromophobe RCC demonstrates vimentin positivity, whereas oncocytoma shows cathepsin H positivity.⁷

In less than 10% of cases, oncocytoma and chromophobe RCC may coexist.^1,4 A few genetic alterations have been reported in association with oncocytomas. These include a deletion of chromosome 1 and the sex chromosomes, as well as a balanced translocation involving the 11q13 region.

Preferred Examination

Computed tomography (CT) scanning of the abdomen, combined with intravenous administration of iodinated contrast medium, is the examination of choice and the best modality for the evaluation of a solid renal mass. This technique assists in the detection and localization of the tumor, and CT scanning may help in characterizing the mass, especially if fat-containing lesions (eg, angiomyolipomas) are present. Additionally, staging of the tumor can be performed to classify the extent of the lesion, regional lymphadenopathy, vascular involvement, and metastases. CT scanning also helps in the detection of calcifications and in the differentiation of a complex cyst from a solid neoplasm.

Limitations of Techniques

The imaging characteristics of oncocytomas and RCCs overlap, and differentiating an oncocytoma from an RCC and other solid renal neoplasms is not always possible with ultrasonography, CT scanning, or magnetic resonance imaging (MRI). The presence of a central scar on CT scans or MRIs and a spoke-wheel pattern of vessels on angiograms are often suggestive of oncocytoma but are not entirely specific.

Differential Diagnoses

Renal Cell Carcinoma

Other Problems to Be Considered

Renal adenoma
Renal capsular sarcoma
Adrenal tumor
Retroperitoneal tumor
Complicated renal cyst (Bosniak type 3 or 4)

Radiography

Findings

Plain radiographic findings are nonspecific, and images may demonstrate a large, soft-tissue mass in the renal area with displacement of the fat planes. Calcification is rare. Excretory urography shows a large mass with a renal-contour abnormality and compression of the collecting system.

Degree of Confidence

The degree of confidence is low for detecting oncocytomas with radiographs.

False Positives/Negatives

False-positive results may arise with any lesion that causes a renal-contour abnormality. Examples include renal cysts, any renal mass, and focal infections. In addition, any retroperitoneal tumor may have a similar appearance. False-negative findings are due to the small size of the tumor and the presence of overlapping bowel.

Computed Tomography

Contrast-enhanced computed tomography (CT) scan of the abdomen obtained during the nephrographic phase. This CT scan shows a well-defined, enhancing mass lesion in the lower pole of the left kidney. A central hypoattenuating stellate scar is seen.

Contrast-enhanced computed tomography (CT) scan of the abdomen obtained during the nephrographic phase. This CT scan shows a well-defined, exophytic, solid mass from the midpole of the left kidney. The mass has an atypical appearance of an oncocytoma, is less attenuating than the renal parenchyma, and does not show a scar.

Findings

On nonenhanced CT scans, oncocytomas appear isoattenuating or slightly hyperattenuating relative to the kidney parenchyma. On contrast-enhanced CT scans that are obtained during the nephrographic phase, the mass appears less attenuating than the renal parenchyma.^10,11

Oncocytomas are well encapsulated and have distinct margins, a smooth contour, and a homogeneous appearance. The tumors may range in size from 3 to 10 cm, and in symptomatic patients, the lesions are most often larger than 5 cm.

A central hypoattenuating scar may be observed in 33% of cases, but this scar cannot be differentiated from the central necrosis commonly found in RCC. With the advent of multisection CT scanning, high-resolution thin sections through the kidneys may improve detection of the central scar.

Calcification, necrosis, and hemorrhage are rare with oncocytomas. Typically, features of a malignant tumor—such as invasion or infiltration into the perinephric fat, collecting system, or vessels—are absent. Likewise, regional lymphadenopathy and metastases are not encountered in patients with oncocytoma. Occasionally, multifocal or bilateral tumors may be found.

Degree of Confidence

The degree of confidence for detecting this tumor with CT scanning is high. However, the degree of confidence in differentiating an oncocytoma from an RCC is low.

False Positives/Negatives

Differentiating an oncocytoma from an RCC and other solid renal tumors is not always possible. The presence of a central scar may help, but necrosis in RCC may mimic this finding.

Magnetic Resonance Imaging

T1-weighted magnetic resonance image (MRI). This MRI shows a homogeneous, hypointense, well-defined mass in the lower pole of the kidney.

T2-weighted magnetic resonance image (MRI) of the kidney. This MRI shows that the lesion is hypointense and has a mildly hyperintense central scar (same patient as in Images above and below).

Contrast-enhanced T1-weighted magnetic resonance image (MRI). This MRI of the kidney shows homogeneous enhancement of the mass with a nonenhancing central scar. Note the lack of any tumoral invasion into the perinephric fat (same patient as in Images above).

Findings

On nonenhanced T1-weighted MRIs, oncocytomas are well-defined, homogeneous masses. They may appear isointense to hypointense relative to the renal cortex. On T2-weighted images, the tumors are typically isointense to slightly hypointense; however, slight T2 hyperintensity has also been reported.¹²

When present, the tumor's scar may be seen as a hypointense, stellate area in the center of the lesion on T1- and T2-weighted MRIs. However, tumor necrosis, a common feature of malignant masses, appears hypointense on T1-weighted images and hyperintense on T2-weighted images. Rarely, the central scar may appear bright on T2-weighted images.

After the intravenous administration of gadopentetate dimeglumine contrast material, oncocytomas show homogeneous enhancement, with a nonenhancing central scar. As discussed in the CT section above, features of an invasive tumor are absent.

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. 

NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.

Degree of Confidence

The degree of confidence with MRIs for detecting this lesion is high, but this technique's degree of confidence is low for making a specific diagnosis.

False Positives/Negatives

Differentiating an oncocytoma from an RCC and other solid renal tumors is not always possible.

Ultrasonography

Findings

On ultrasonography images, oncocytomas appear as well-defined, homogeneous, and hypoechoic to isoechoic masses. The central scar cannot be confidently identified on sonograms; however, when the scar is seen, especially in large lesions, it may appear echogenic. Color Doppler ultrasonography may show central radiating vessels. As discussed in the CT scanning and MRI sections above, the features of an invasive tumor are conspicuously absent.¹³

Degree of Confidence

Ultrasonography has low sensitivity and specificity in the detection and characterization of solid renal masses. However, this modality is useful for differentiating a solid mass from a complex cystic mass.

False Positives/Negatives

Small isoechoic lesions may be missed on sonograms. Larger lesions cannot be differentiated from other renal masses.

Nuclear Imaging

Findings

Scintigraphy is not routinely performed in the evaluation of renal tumors. On technetium-99m (^99m Tc) dimercaptosuccinic acid (DMSA) scans, the oncocytoma appears as a photopenic area that displaces the renal cortex and collecting system.

On fluorodeoxyglucose (FDG) positron emission tomography (PET) scans, oncocytomas usually have less FDG uptake than RCCs. The amount of uptake is usually isointense relative to the renal parenchyma. However, oncocytomas can occasionally have uptake in the range similar to that of RCC uptake.

Degree of Confidence

The degree of confidence with nuclear medicine is low.

False Positives/Negatives

False-positive results are due to renal cysts or other photopenic renal masses. False-negative results occur if the mass is small or if the lesion does not cause a renal-contour abnormality.

Angiography

Findings

With the advent of CT scanning, routine angiography is not performed to diagnose renal masses. However, the classic angiographic findings for oncocytomas include a spoke-wheel arrangement of tumoral vessels, homogeneous tumoral contrast during the capillary phase, sharp demarcation from the kidney and surrounding areas, and a peritumoral halo (lucent-rim sign). Bizarre neoplastic vessels are conspicuously absent, which is in contrast to RCC.

Degree of Confidence

The degree of confidence with angiography is low.

False Positives/Negatives

Hypovascular lesions may result in false-negative results, and hypervascular lesions may mimic RCCs.

Intervention

Medicolegal Pitfalls

• Statistically, RCC is the most common solid renal mass.
• Infrequently, benign tumors such as oncocytoma are encountered.
• Because of the overlap in imaging features and histologic appearances between oncocytomas and RCCs, accurate differentiation on preoperative imaging or percutaneous biopsy remains difficult.
• The diagnosis is often retrospectively established by means of gross pathology and microscopy with special stains.

Special Concerns

• In select patient populations in whom surgery is not suitable, such as the elderly and those patients with extensive comorbid conditions, percutaneous needle biopsy may be useful to diagnose oncocytoma.
• Once the diagnosis is confirmed, the lesions may be followed up with observation.

Multimedia

Media file 1: Contrast-enhanced computed tomography (CT) scan of the abdomen obtained during the nephrographic phase. This CT scan shows a well-defined, enhancing mass lesion in the lower pole of the left kidney. A central hypoattenuating stellate scar is seen.

Media file 2: Contrast-enhanced computed tomography (CT) scan of the abdomen obtained during the nephrographic phase. This CT scan shows a well-defined, exophytic, solid mass from the midpole of the left kidney. The mass has an atypical appearance of an oncocytoma, is less attenuating than the renal parenchyma, and does not show a scar.

Media file 3: T1-weighted magnetic resonance image (MRI). This MRI shows a homogeneous, hypointense, well-defined mass in the lower pole of the kidney.

Media file 4: T2-weighted magnetic resonance image (MRI) of the kidney. This MRI shows that the lesion is hypointense and has a mildly hyperintense central scar (same patient as in Images above and below).

Media file 5: Contrast-enhanced T1-weighted magnetic resonance image (MRI). This MRI of the kidney shows homogeneous enhancement of the mass with a nonenhancing central scar. Note the lack of any tumoral invasion into the perinephric fat (same patient as in Images above).

References

1. Schatz SM, Lieber MM. Update on oncocytoma. Curr Urol Rep. Feb 2003;4(1):30-5. [Medline].

2. Zippel L. Zur kenntnis der onkocyten. Virchows Arch Pathol Anat Histopathol. 1942;308:360–82.

3. Klein MJ, Valensi QJ. Proximal tubular adenomas of kidney with so-called oncocytic features. A clinicopathologic study of 13 cases of a rarely reported neoplasm. Cancer. 1976;38:906-14. [Medline].

4. Dechet CB, Bostwick DG, Blute ML, Bryant SC, Zincke H. Renal oncocytoma: multifocality, bilateralism, metachronous tumor development and coexistent renal cell carcinoma. J Urol. Jul 1999;162(1):40-2. [Medline].

5. Snyder ME, Bach A, Kattan MW, et al. Incidence of benign lesions for clinically localized renal masses smaller than 7 cm in radiological diameter: influence of sex. J Urol. Dec 2006;176(6 Pt 1):2391-5; discussion 2395-6. [Medline].

6. de la Cruz Burgos R, Martel Villagrán J. [Renal oncocytoma. Fundamental radiologic manifestations and enhancement patterns in tri-phase helical CT] [Spanish]. Radiologia. Mar-Apr 2007;49(2):109-14. [Medline].

7. Algaba F. Renal adenomas: pathological differential diagnosis with malignant tumors. Adv Urol. 2008;974848. [Medline].

8. Hruby GW, Fine JK, Landman J. Ultrasound-guided percutaneous ablation of a renal mass in a renal allograft. Urology. Oct 2006;68(4):891.e5-6. [Medline].

9. Bahrami A, Schwartz MR, Ayala AG, Goldfarb RA, Brady JR, Takei H. Concurrent angiomyolipoma and two oncocytomas in the same kidney. Ann Diagn Pathol. Apr 2007;11(2):132-6. [Medline].

10. Mistry R, Manikandan R, Williams P, Philip J, Littler P, Foster CS, et al. Implications of computer tomography measurement in the management of renal tumours. BMC Urol. Nov 4 2008;8:13. [Medline].

11. Prasad SR, Surabhi VR, Menias CO, Raut AA, Chintapalli KN. Benign renal neoplasms in adults: cross-sectional imaging findings. AJR Am J Roentgenol. Jan 2008;190(1):158-64. [Medline].

12. Pedrosa I, Sun MR, Spencer M, Genega EM, Olumi AF, Dewolf WC, et al. MR imaging of renal masses: correlation with findings at surgery and pathologic analysis. Radiographics. Jul-Aug 2008;28(4):985-1003. [Medline].

13. Fan L, Lianfang D, Jinfang X, Yijin S, Ying W. Diagnostic efficacy of contrast-enhanced ultrasonography in solid renal parenchymal lesions with maximum diameters of 5 cm. J Ultrasound Med. Jun 2008;27(6):875-85. [Medline].

14. Chao DH, Zisman A, Pantuck AJ, et al. Changing concepts in the management of renal oncocytoma. Urology. May 2002;59(5):635-42. [Medline].

15. Davidson AJ, Hayes WS, Hartman DS, McCarthy WF, Davis CJ Jr. Renal oncocytoma and carcinoma: failure of differentiation with CT. Radiology. Mar 1993;186(3):693-6. [Medline]. [Full Text].

16. Kutikov A, Fossett LK, Ramchandani P, et al. Incidence of benign pathologic findings at partial nephrectomy for solitary renal mass presumed to be renal cell carcinoma on preoperative imaging. Urology. Oct 2006;68(4):737-40. [Medline].

17. Newhouse JH, Wagner BJ. Renal oncocytomas. Abdom Imaging. May-Jun 1998;23(3):249-55. [Medline].

18. Pretorius ES, Siegelman ES, Ramchandani P, Cangiano T, Banner MP. Renal neoplasms amenable to partial nephrectomy: MR imaging. Radiology. Jul 1999;212(1):28-34. [Medline]. [Full Text].

Keywords

oncocytoma of the kidney, benign renal tumor, renal neoplasms, renal cell carcinomas, RCCs

Contributor Information and Disclosures

Author

Sanjeeva P Kalva, MD, Assistant Radiologist, Massachusetts General Hospital, Instructor in Radiology, Harvard Medical School, Department of Radiology, Massachusetts General Hospital
Sanjeeva P Kalva, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Cordis Endovascular Honoraria Speaking and teaching; Cook Grant/research funds Other; Cordis Grant/research funds Other; Angiodynamics Grant/research funds None

Coauthor(s)

Dushyant Sahani, MD, Clinical Instructor of Abdominal Radiology and Intervention, Harvard Medical School; Assistant Radiologist, Department of Abdominal Imaging and Intervention, Massachusetts General Hospital
Disclosure: Nothing to disclose.

Medical Editor

Steven Perlmutter, MD, FACR, Associate Professor of Clinical Radiology, School of Medicine at Stony Brook University; Medical Director of Radiology, Peconic Bay Medical Center
Steven Perlmutter, MD, FACR is a member of the following medical societies: American College of Radiology, American Institute of Ultrasound in Medicine, American Medical Association, American Roentgen Ray Society, Association of Program Directors in Radiology, Association of University Radiologists, Medical Society of the State of New York, Radiological Society of North America, Society of Breast Imaging, Society of Nuclear Medicine, and Society of Uroradiology
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

Managing Editor

Arnold C Friedman, MD, FACR, Associate Chairman, Department of Radiology, University of Florida Health Science Center; Chief, Department of Radiology, Shands-Jacksonville Hospital
Arnold C Friedman, MD, FACR is a member of the following medical societies: American College of Radiology, American Institute of Ultrasound in Medicine, American Roentgen Ray Society, Association of University Radiologists, and Radiological Society of North America
Disclosure: Nothing to disclose.

CME Editor

Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

Eugene C Lin, MD, Consulting Radiologist, Virginia Mason Medical Center; Clinical Assistant Professor of Radiology, University of Washington School of Medicine
Eugene C Lin, MD is a member of the following medical societies: American College of Nuclear Medicine, American College of Radiology, Radiological Society of North America, and Society of Nuclear Medicine
Disclosure: Nothing to disclose.

Related eMedicine topics:

Renal Cell Carcinoma

Clear Cell Sarcoma of the Kidney

Polycystic Kidney Disease

Cystic Diseases of the Kidney

Acquired Cystic Kidney Disease

Guidelines:

Indeterminate Renal Masses

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