Renal oncocytoma CT

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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

Abdonimal CT scan is helpful in the diagnosis of renal oncocytoma.

CT

On abdominal CT scan, renal oncocytoma is characterized by a large well demarcated tumor.

Noncontrast CT Scan

• Homogenous attenuation: If tumor size is less than 3 cm
• Heterogenous attenuation: If tumor size is more than 3 cm
• Perinephric fat-stranding may be present due to edema
• Calcification may be present

Contrast CT Scan

• Small tumors may enhance homogeneously, but usually, enhancement is heterogeneous and the mass is larger.
• Central stellate non-enhancing scar is seen in approximately a third of cases.
• Renal vein thrombosis may be present, but tumor thrombus is absent.

Overview

There are no CT scan findings associated with [disease name].

OR

[Location] CT scan may be helpful in the diagnosis of [disease name]. Findings on CT scan suggestive of/diagnostic of [disease name] include [finding 1], [finding 2], and [finding 3].

OR

There are no CT scan findings associated with [disease name]. However, a CT scan may be helpful in the diagnosis of complications of [disease name], which include [complication 1], [complication 2], and [complication 3].

CT scan

There are no CT scan findings associated with [disease name].

OR

[Location] CT scan may be helpful in the diagnosis of [disease name]. Findings on CT scan suggestive of/diagnostic of [disease name] include:

• [Finding 1]
• [Finding 2]
• [Finding 3]

OR

There are no CT scan findings associated with [disease name]. However, a CT scan may be helpful in the diagnosis of complications of [disease name], which include:

• [Complication 1]
• [Complication 2]
• [Complication 3]

solid, homogenous lesion that can demonstrate a centrally located stellate area of low attenuation, indicative of a central scar.8–10,45,46 Most studies have shown that oncocytomas are hypodense relative to normal renal parenchyma on CT with and without contrast.9,45,47 Tumor homogeneity has been observed in 50% to 100% of tumors.9,45 The examination of comparable RCC lesions showed that 22% also appear homogenous on CT. Davidson et al.46 used the CT criteria of homogeneity alone or with the presence of a centrally located stellate area of low attenuation to distinguish oncocytomas from RCC. Overall, 67% of oncocytomas were given readings that were consistent with the correct diagnosis. More importantly, 42% of adenocarcinomas less than 3 cm and 16% of tumors larger than 3 cm were also read as oncocytomas. The study concluded that CT findings lacked sufficient predictive value in distinguishing benig tumors from malignant ones. The inadequacy of CT was reaffirmed in a consensus conference at which radiologists, pathologists, and urologists attempted to establish CT criteria for the diagnosis of oncocytoma.48 Seven cases were read by seven radiologists, and oncocytoma was correctly diagnosed in 6 (12%) of 49 observations.

In general, it is not possible to differentiate preoperatively renal oncocytomas from the other renal carcinomas by radiological imaging techniques. Such resemblance might lead to radical nephrectomy, as until now almost all renal oncocytomas were considered to be typical RCCs and therefore most patients were treated by total nephrectomy.

Oncocytomas are usually asymptomatic and are often discovered incidentally on cross-sectional imaging performed for other indications. Much research is under way to determine a way to distinguish oncocytoma from renal cell carcinoma by imaging and, therefore, to potentially avoid surgery for a benign tumor (63–65). Although frequently associated with a central scar and hypervascularity, these findings are not sufficient to make a definitive diagnosis of oncocytoma (66). With the increased use of cross-sectional imaging, renal masses are being identified much more frequently with concomitant overtreatment of benign neoplasms, such as oncocytoma (67). Currently, there are no precise radiologic criteria for oncocytoma. Recent work has shown promising results for the use of technetium-99m (99mTc)-sestamibi single-photon emission computed tomography/x-ray computed tomography (SPECT/CT) to differentiate oncocytomas and hybrid oncocytic/ chromophobe tumors from other renal cell carcinomas (68). In an updated series of cases, this new modality showed an overall sensitivity of 87.5% and a specificity of 95.2% (69).