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.
Natural history and presentationOncocytomas originate from the intercalated cells of the renal collecting duct. On gross pathologic examination, the tumors appear spherical and are large (average size, 7 cm),5 with a pseudocapsule. On cut sections, oncocytomas appear homogeneous, with a mahogany color—in contrast to yellow renal cell carcinomas (RCCs). A fleshy central scar, which is a characteristic finding of oncocytomas,6 may be observed in 33-54% of such tumors. Necrosis, hemorrhage, and calcification, however, are rare findings.
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.
Approximately 56-91% of the oncocytomas are incidentally detected on imaging studies that have been performed for another indication.4,8,9 However, 17-21% of affected patients present with symptoms such as hematuria, flank pain, and an abdominal mass. In patients who present with symptoms, hematuria is more common than masslike findings.Treatment
Percutaneous renal biopsy, fine-needle aspiration cytology, and frozen-section biopsy have been used with variable success for the differentiation of oncocytoma from RCC. Because of these limitations in preoperative pathologic evaluation, the consensus among clinicians is to treat a solid renal mass with a partial or total nephrectomy.
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
Other Problems to Be Considered
Renal adenoma
Renal capsular sarcoma
Adrenal tumor
Retroperitoneal tumor
Complicated renal cyst (Bosniak type 3 or 4)
More on Oncocytoma, Kidney |
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| References |
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References
Schatz SM, Lieber MM. Update on oncocytoma. Curr Urol Rep. Feb 2003;4(1):30-5. [Medline].
Zippel L. Zur kenntnis der onkocyten. Virchows Arch Pathol Anat Histopathol. 1942;308:360–82.
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].
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].
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].
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].
Algaba F. Renal adenomas: pathological differential diagnosis with malignant tumors. Adv Urol. 2008;974848. [Medline].
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].
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].
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].
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].
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].
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].
Chao DH, Zisman A, Pantuck AJ, et al. Changing concepts in the management of renal oncocytoma. Urology. May 2002;59(5):635-42. [Medline].
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].
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].
Newhouse JH, Wagner BJ. Renal oncocytomas. Abdom Imaging. May-Jun 1998;23(3):249-55. [Medline].
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].
Further Reading
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
Keywords
oncocytoma of the kidney, benign renal tumor, renal neoplasms, renal cell carcinomas, RCCs
