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Imaging findings of common benign renal tumors in the era of small renal masses: differential diagnosis from small renal cell carcinoma: current status and future perspectives.

Woo S, Cho JY - Korean J Radiol (2015)

Bottom Line: The prevalence of small renal masses (SRM) has risen, paralleling the increased usage of cross-sectional imaging.Therefore, differentiation between early renal cell carcinoma (RCC) and benign SRM is critical to achieve proper management.Furthermore, the role of percutaneous biopsy is discussed as imaging is yet imperfect, therefore necessitating biopsy in certain circumstances to confirm the benignity of SRMs.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Seoul National University College of Medicine, Seoul 110-744, Korea.

ABSTRACT
The prevalence of small renal masses (SRM) has risen, paralleling the increased usage of cross-sectional imaging. A large proportion of these SRMs are not malignant, and do not require invasive treatment such as nephrectomy. Therefore, differentiation between early renal cell carcinoma (RCC) and benign SRM is critical to achieve proper management. This article reviews the radiological features of benign SRMs, with focus on two of the most common benign entities, angiomyolipoma and oncocytoma, in terms of their common imaging findings and differential features from RCC. Furthermore, the role of percutaneous biopsy is discussed as imaging is yet imperfect, therefore necessitating biopsy in certain circumstances to confirm the benignity of SRMs.

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year-old man with small angiomyolipoma with minimal fat in right kidney demonstrating typical CT and MR findings.A. Axial precontrast CT scan reveals oval shaped 1.8-cm sized hyperdense mass (arrow) in right kidney upper pole. At region of interest measurement, attenuation of mass was 51 Hounsfield units (HU) while renal parenchyma was measured as 39 HU. B, C. Axial corticomedullary phase (B) and early excretory phase (C) CT scan shows that mass (arrow) is less enhanced compared with renal parenchyma. D. Renal mass (arrow) demonstrates low signal intensity (SI) compared with renal parenchyma on coronal T2-weighted image. E, F. On coronal chemical shift MR imaging, suspicious focus (arrow) of SI drop from in phase (E) to opposed phase (F) is noted. G-I. Coronal contrast-enhanced MRI shows that mass (arrow) is less enhanced than background renal parenchyma.
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Figure 2: year-old man with small angiomyolipoma with minimal fat in right kidney demonstrating typical CT and MR findings.A. Axial precontrast CT scan reveals oval shaped 1.8-cm sized hyperdense mass (arrow) in right kidney upper pole. At region of interest measurement, attenuation of mass was 51 Hounsfield units (HU) while renal parenchyma was measured as 39 HU. B, C. Axial corticomedullary phase (B) and early excretory phase (C) CT scan shows that mass (arrow) is less enhanced compared with renal parenchyma. D. Renal mass (arrow) demonstrates low signal intensity (SI) compared with renal parenchyma on coronal T2-weighted image. E, F. On coronal chemical shift MR imaging, suspicious focus (arrow) of SI drop from in phase (E) to opposed phase (F) is noted. G-I. Coronal contrast-enhanced MRI shows that mass (arrow) is less enhanced than background renal parenchyma.

Mentions: CT has been more meticulously studied with regard to small AML with minimal fat. One of the most representative findings of AML with minimal fat on CT is the extent of hyperattenuation compared with the renal parenchyma. It was found to be significantly more common in these AMLs (53%) than in RCCs (13%) (24). This finding has also been confirmed upon quantitative analysis with thresholds of > 38.5 HU and > 37 HU to differentiate small AML with minimal fat from RCC and non-clear cell type RCC, respectively, resulting insensitivities and specificities up to 91.7% and 76.4%, respectively (Fig. 2) (25, 26, 27). A different approach that has been thoroughly examined is attenuation measurement using histogram analysis on unenhanced CT. Although earlier studies reported promising results with a high specificity (100%) and positive predictive value (100%) (28), further research by different investigators led to the realization that pixel histogram analysis cannot reliably differentiate between AML with minimal fat and RCC, or at least between AML with minimal fat and clear cell RCC (29, 30).


Imaging findings of common benign renal tumors in the era of small renal masses: differential diagnosis from small renal cell carcinoma: current status and future perspectives.

Woo S, Cho JY - Korean J Radiol (2015)

year-old man with small angiomyolipoma with minimal fat in right kidney demonstrating typical CT and MR findings.A. Axial precontrast CT scan reveals oval shaped 1.8-cm sized hyperdense mass (arrow) in right kidney upper pole. At region of interest measurement, attenuation of mass was 51 Hounsfield units (HU) while renal parenchyma was measured as 39 HU. B, C. Axial corticomedullary phase (B) and early excretory phase (C) CT scan shows that mass (arrow) is less enhanced compared with renal parenchyma. D. Renal mass (arrow) demonstrates low signal intensity (SI) compared with renal parenchyma on coronal T2-weighted image. E, F. On coronal chemical shift MR imaging, suspicious focus (arrow) of SI drop from in phase (E) to opposed phase (F) is noted. G-I. Coronal contrast-enhanced MRI shows that mass (arrow) is less enhanced than background renal parenchyma.
© Copyright Policy - open-access
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Figure 2: year-old man with small angiomyolipoma with minimal fat in right kidney demonstrating typical CT and MR findings.A. Axial precontrast CT scan reveals oval shaped 1.8-cm sized hyperdense mass (arrow) in right kidney upper pole. At region of interest measurement, attenuation of mass was 51 Hounsfield units (HU) while renal parenchyma was measured as 39 HU. B, C. Axial corticomedullary phase (B) and early excretory phase (C) CT scan shows that mass (arrow) is less enhanced compared with renal parenchyma. D. Renal mass (arrow) demonstrates low signal intensity (SI) compared with renal parenchyma on coronal T2-weighted image. E, F. On coronal chemical shift MR imaging, suspicious focus (arrow) of SI drop from in phase (E) to opposed phase (F) is noted. G-I. Coronal contrast-enhanced MRI shows that mass (arrow) is less enhanced than background renal parenchyma.
Mentions: CT has been more meticulously studied with regard to small AML with minimal fat. One of the most representative findings of AML with minimal fat on CT is the extent of hyperattenuation compared with the renal parenchyma. It was found to be significantly more common in these AMLs (53%) than in RCCs (13%) (24). This finding has also been confirmed upon quantitative analysis with thresholds of > 38.5 HU and > 37 HU to differentiate small AML with minimal fat from RCC and non-clear cell type RCC, respectively, resulting insensitivities and specificities up to 91.7% and 76.4%, respectively (Fig. 2) (25, 26, 27). A different approach that has been thoroughly examined is attenuation measurement using histogram analysis on unenhanced CT. Although earlier studies reported promising results with a high specificity (100%) and positive predictive value (100%) (28), further research by different investigators led to the realization that pixel histogram analysis cannot reliably differentiate between AML with minimal fat and RCC, or at least between AML with minimal fat and clear cell RCC (29, 30).

Bottom Line: The prevalence of small renal masses (SRM) has risen, paralleling the increased usage of cross-sectional imaging.Therefore, differentiation between early renal cell carcinoma (RCC) and benign SRM is critical to achieve proper management.Furthermore, the role of percutaneous biopsy is discussed as imaging is yet imperfect, therefore necessitating biopsy in certain circumstances to confirm the benignity of SRMs.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Seoul National University College of Medicine, Seoul 110-744, Korea.

ABSTRACT
The prevalence of small renal masses (SRM) has risen, paralleling the increased usage of cross-sectional imaging. A large proportion of these SRMs are not malignant, and do not require invasive treatment such as nephrectomy. Therefore, differentiation between early renal cell carcinoma (RCC) and benign SRM is critical to achieve proper management. This article reviews the radiological features of benign SRMs, with focus on two of the most common benign entities, angiomyolipoma and oncocytoma, in terms of their common imaging findings and differential features from RCC. Furthermore, the role of percutaneous biopsy is discussed as imaging is yet imperfect, therefore necessitating biopsy in certain circumstances to confirm the benignity of SRMs.

Show MeSH
Related in: MedlinePlus