Renal oncocytoma: report of a case with bilateral multifocal oncocytomas

Renal oncocytomas are uncommon, benign tumors that classically are treated by local excision or heminephrectomy. Preoperative differentiation from renal cell carcinoma is invaluable in the planning of treatment. Cases of renal oncocytoma treated conservatively have been reported. This is a case report of bilateral multifocal renal oncocytomas of which only three previous cases have been reported. Diagnosis was made from multiple fine needle biopsies and present treatment consists only of conservative observation.     

Incidental Bilateral Renal Oncocytoma in a Patient with Metastatic Carcinoma of Unknown Primary: a Pitfall on 18F-FDG PET/CT

Bilateral renal masses are uncommon but can raise a strong suspicion of primary or secondary malignancy, especially during the initial work-up of an oncology patient. Renal oncocytomas are benign renal tumors that are commonly discovered incidentally on diagnostic imaging with a small percentage occurring bilaterally. Although ¹⁸F-FDG uptake in renal oncocytomas has been described, a case of a bilateral ¹⁸F-FDG-avid renal oncocytoma has not been previously reported in the literature. A variety of malignant causes of bilateral ¹⁸F-FDG positive renal masses are known, however it is important to include this benign etiology in the differential diagnosis. We report an unusual case of an incidental bilateral renal oncocytoma evaluated with contrast enhanced CT and ¹⁸F-FDG PET/CT.     

Radiologic findings in renal oncocytoma

The imaging findings of 36 renal oncocytomas in 32 patients were evaluated retrospectively. Twenty-two patients underwent ultrasound (US), 16 CT, 25 angiography, 19 urography, and 6 fine-needle biopsy. At US 8 of the oncocytomas were isoechoic, 7 hyperechoic, and 7 hypoechoic. The structure was homogeneous in 59% and nonhomogeneous in 41%. At plain CT 12 oncocytomas were homogeneously hypodense, 3 isodense, and one hyperdense. Contrast enhancement was homogeneous in 10 and inhomogeneous in 4 cases. A stellate scar was detected in one case, and in one case a contrast study was not performed. At angiography the oncocytomas were hypervascular in 21, hypovascular in 3 cases, and one was not detected. Nineteen of the tumors were well delineated. A spokewheel arterial pattern was detected in 3 tumors. The cytologic diagnosis was benign renal oncocytoma in 4 cases and highly suggestive of oncocytoma in 2 cases. We conclude that the homogeneity of a renal tumor at US and at CT may suggest the possibility of oncocytoma. US-guided fine-needle biopsy is a useful diagnostic tool in patients who need a precise presurgical diagnosis.     

Small renal neoplasms: clinical, pathologic, and imaging features

Small renal neoplasms are being found more often because of the widespread use of abdominal CT and sonography. Little is known about their natural history. We therefore retrospectively reviewed clinical, pathologic, and imaging findings in 22 patients with surgically confirmed solitary renal neoplasms that were 3 cm or less in diameter. Eighteen lesions were first found by CT, three by sonography, and one by IV urography. Three lesions were discovered because the patients had hematuria. Nineteen were incidental radiologic diagnoses in patients without renal symptoms. Of 22 neoplasms, 15 (68%) were renal cell carcinomas, six (27%) were oncocytomas, and one (5%) was a lymphoma. Fourteen (93%) of the 15 carcinomas were confined to the kidney, and one showed microscopic capsular invasion. Metastases did not develop in any patient with carcinoma, indicating that small carcinomas usually have good prognoses. Patients with carcinomas had a mean follow-up of 42 months. All neoplasms were visible on CT. However, characterization of these lesions sometimes required a combination of CT and sonography and occasionally angiography. The carcinomas, oncocytomas, and solitary renal lymphoma could not be distinguished radiologically. Small renal neoplasms are most often found incidentally by CT performed in patients without renal complaints. Most are low-stage carcinomas, and some are oncocytomas.     

Unusual renal oncocytomas: Pathologic and CT correlations

The unusual features of nine oncocytomas in five patients are reported herein. These include multiplicity in two, bilaterality in two, calcification in one, and association with renal cell carcinomas in three patients. Radiologists should be aware of these findings for this benign renal neoplasm.     

Unusual renal oncocytomas: pathologic and CT correlations.

The unusual features of nine oncocytomas in five patients are reported herein. These include multiplicity in two, bilaterality in two, calcification in one, and association with renal cell carcinomas in three patients. Radiologists should be aware of these findings for this benign renal neoplasm.     

Computed tomographic and angiographic findings in renal oncocytoma

Nine cases with histologically proven renal oncocytoma are presented. In all cases, ultrasonography gave the first indication of a tumour and intravenous urography was tumour-specific in only six, whilst angiography was so in only four of the cases with peripheral extension beyond the normal organ limits. Examination by computed tomography showed retrospectively, in the three cases with smaller oncocytomas up to 3 cm in diameter, findings that seemed promisingly characteristic: without contrast medium, the tumour appeared homogeneously hyperdense in comparison with normal renal parenchyma, but homogeneously hypodense after injection of contrast medium. One of the smaller oncocytomas, however, showed regions of heterogeneity both with and without contrast medium. Only one oncocytoma of 4 cm diameter presented the central stellate, low-attenuation "scar" described by Quinn et al. The angiographic criteria cited by Ambos were fulfilled in only three of the larger oncocytomas. In four of the cases, the tumour was enucleated and the organ left in situ on the basis of frozen section diagnosis. Those patients with tumours extending outside the organ or those of questionable diagnosis on frozen section were treated by nephrectomy. In one patient, the pathologist suspected metastasis from the thyroid; hemithyroidectomy confirmed on oncocytic adenoma of the left thyroid lobe.     

Renal oncocytoma: Further observations and literature review

Although controversy exists among pathologists regarding the existence of a benign renal adenoma of proximal tubular origin (oncocytoma), certain “typical” angiographic features have been proported to characterize such renal masses. These include “spoke-wheel” vasculature, homogeneous blush, orderly vascular pattern, and absence of vascular puddling or venous shunting. These features may characterize oncocytomas but may also be shared by an occasional renal cell carcinoma. Nonetheless, their demonstration should alert radiologists and surgeons to the possibility that a given renal mass may be a benign oncocytoma. Such a presumptive diagnosis may have significant surgical implications.     

Diffusion-weighted imaging versus contrast-enhanced MR imaging for the differentiation of renal oncocytomas and chromophobe renal cell carcinomas

Objectives

To compare the performance of diffusion-weighted imaging (DWI) with that of contrast-enhanced MRI in differentiating renal oncocytomas from chromophobe renal cell carcinomas (RCCs).

Methods

We recruited 48 patients with histopathologically confirmed renal oncocytomas (n=16) and chromophobe RCCs (n=32). All patients underwent preoperative DWI and contrast-enhanced MRI. Apparent diffusion coefficient (ADC) and signal intensity were measured in each patient. ADC ratio and percentage of signal intensity change were calculated.

Results

Mean ADC values for renal oncoctytomas were significantly higher than those for chromophobe RCCs (1.59±0.21 vs. 1.09±0.29× 10^?3 mm²/s, p < 0.001). Area under the ROC curve, sensitivity and specificity were 0.931, 87.5% and 84.4%, respectively, for ADC measurement of DW imaging; 0.825, 87.5% and 75%, respectively, for enhancement ratio (p > 0.05). Adding ADC values to the enhancement ratios in the ROC, analysis to differentiate renal oncocytoma from chromophobe RCCs increased specificity from 75 to 87.5% at 87.5% sensitivity without significantly increasing the AUC (0.930).

Conclusions

Both DWI and contrast-enhanced MRI may assist in differentiating renal oncocytomas from chromophobe RCCs, with DWI showing higher diagnostic value. The combination of the two parameters could potentially provide better performance in distinguishing these two tumours.

Key Points

? ADC values can assist in differentiating renal oncocytomas from chromophobe RCCs. ? DW imaging possesses better specificity than does contrast-enhanced MR imaging. ? Combining the two parameters provides higher specificity regarding the differential diagnosis.

     

Routinely performed multiparametric magnetic resonance imaging helps to differentiate common subtypes of renal tumours

Objectives

To retrospectively evaluate the ability of multiparametric magnetic resonance (MR) imaging to differentiate renal tumours.

Methods

MR images from 100 consecutive pathologically proven solid renal tumours without macroscopic fat [57 clear cell, 16 papillary and 7 chromophobe renal cell carcinomas (RCCs), 16 oncocytomas and 4 minimal fat angiomyolipomas (AMLs)] between 2009 and 2012 were evaluated. Two radiologists blinded to pathology results independently reviewed double-echo chemical shift, dynamic contrast-enhanced T1- and T2-weighted images and apparent diffusion coefficient (ADC) maps. Signal intensity index (SII), tumour-to-spleen SI ratio (TSR), ADC ratio, wash-in (WiI) and wash-out indices (WoI) between different phases were calculated.

Results

There were significant differences between papillary RCCs and other renal tumours for arterial WiI (P?<?0.001), initial WoI (P?=?0.006) and ADC ratio (P?<?0.001); between chromophobe RCCs and oncocytomas for TSR (P?=?0.02), parenchymal WiI (P?=?0.03), late WiI (P?=?0.02), initial WoI (P?=?0.03) and late WoI (P?=?0.04); and between clear cell RCCs and oncocytomas for SII (P?=?0.01) and parenchymal WiI (P?=?0.01). Papillary RCCs were distinguished from other tumours (sensitivity 37.5 %, specificity 100 %) and oncocytomas from chromophobe RCCs (sensitivity 25 %, specificity 100 %) and clear cell RCCs (sensitivity 100 %, specificity 94.2 %).

Conclusion

MR imaging provides criteria able to accurately distinguish papillary RCCs from other tumours and oncocytomas from chromophobe and clear cell RCCs.

Key Points

? Multiparametric MR parameters accurately distinguish papillary RCCs with high specificity (100 %). ? Oncocytomas can be distinguished from chromophobe RCCs with high specificity (100 %). ? Oncocytomas can be distinguished from clear cell RCCs with high specificity (94.2 %). ? In oncocytomatosis, imaging follow-up with such parameters analysis could be promoted.     

Renal oncocytoma. Ultrasonographic study of 4 cases

The authors report four cases of renal oncocytoma investigated by echography and proved by histology after surgery. Describing the clinical cases, after a brief review of the literature, the radiologic findings are analysed with particular regard to the sonographic signs that can preoperatively differentiate oncocytomas from carcinomas. The authors conclude that the only sonographic distinguishing feature is a quite characteristic central hyperechoic streak corresponding to the fibrous scar, frequently found in this benign tumor.     

肾嗜酸细胞腺瘤的CT表现与病理对照分析

目的探讨肾嗜酸细胞腺瘤的CT表现与病理对照分析,以提高对本病的认识。方法回顾性分析经病理证实的8例肾嗜酸细胞腺瘤患者的影像与病理资料。8例均行CT平扫及多期增强扫描,包括肾皮质期、髓质期和排泄期。结果 CT平扫示8例患者均为单发,7例位于右肾,1例位于左肾,最大径3.9～13.0cm,平均5.9cm,均大于3cm,1例可见钙化。增强扫描:皮质期8例病灶均明显强化。髓质期7例病灶持续强化,8例病灶内可见"星芒状"瘢痕,6例有相对完整假包膜。结论肾嗜酸细胞腺瘤的CT表现与病理表现有相关性,CT表现典型者可作出正确诊断。     

Diffusion-weighted imaging of focal renal lesions: a meta-analysis

Objectives

Contrast-enhanced MRI can only distinguish to a limited extent between malignant and benign focal renal lesions. The aim of this meta-analysis is to review renal diffusion-weighted imaging (DWI) to compare apparent diffusion coefficient (ADC) values for different renal lesions that can be applied in clinical practice.

Methods

A PubMed search was performed to identify relevant articles published 2004–2011 on renal DWI of focal renal lesions. ADC values were extracted by lesion type to determine whether benign or malignant. The data table was finalised in a consensus read. ADC values were evaluated statistically using meta-regression based on a linear mixed model. Two-sided P value <5 % indicated statistical significance.

Results

The meta-analysis is based on 17 studies with 764 patients. Renal cell carcinomas have significant lower ADC values than benign tissue (1.61?±?0.08?×?10^-3 mm²/s vs 2.10?±?0.09?×?10^-3 mm²/s; P?<?0.0001). Uroepithelial malignancies can be differentiated by lowest ADC values (1.30?±?0.11?×?10^-3 mm²/s). There is a significant difference between ADC values of renal cell carcinomas and oncocytomas (1.61?±?0.08?×?10^-3 mm²/s vs 2.00?±?0.08?×?10^-3 mm²/s; P?<?0.0001).

Conclusions

Evaluation of ADC values can help to determine between benign and malignant lesions in general but also seems able to differentiate oncocytomas from malignant tumours, hence potentially reducing the number of unnecessarily performed nephrectomies.

Key Points

? This meta-analysis assesses the role of diffusion-weighted MRI in renal lesions. ? ADC values obtained by DW MRI have been compared for different renal lesions. ? ADC values can help distinguish between benign and malignant tumours. ? Differentiating oncocytomas from malignant tumours can potentially reduce inappropriate nephrectomies.     

Solid renal cortical tumors: differentiation with CT

PURPOSE: To retrospectively determine if solid renal cortical tumors can be differentiated on computed tomographic (CT) images on the basis of their morphologic features and enhancement patterns. MATERIALS AND METHODS: Institutional review board approval was obtained and the informed consent requirement was waived for this HIPAA-compliant study. Between January 2004 and September 2005, 193 consecutive patients (age range, 19-95 years; 112 men, 81 women) with renal masses underwent total or partial nephrectomy and preoperative renal CT. Two radiologists retrospectively reviewed CT studies in an independent and blinded fashion. The pattern and degree of enhancement, lesion contour, presence of neovascularity, and calcifications were evaluated. Fisher exact tests, Pearson chi(2) tests, multivariate logistic regression, and Wilcoxon rank sum tests were performed. RESULTS: Of the 198 renal tumors (median size, 3.4 cm; range, 1.1-20.0 cm) included in this study, 108 (55%) were clear cell renal cell carcinomas (RCCs); 30 (15%), papillary lesions; 24 (12%), chromophobe adenomas; 14 (7%), oncocytomas; six (3%), lipid-poor angiomyolipomas; and 16 (8%), other or unclassified renal tumors. Clear cell RCC most commonly manifested with a mixed enhancement pattern of both hypervascular soft-tissue components and low-attenuation areas that corresponded to necrotic or cystic changes (reader 1, 88% of clear cell tumors; reader 2, 79% of clear cell tumors). This pattern was highly predictive of clear cell RCC (odds ratio of 22 and 54 for readers 1 and 2, respectively, for comparison with homogeneous pattern), whereas the homogeneous and peripheral enhancing patterns were more predictive of less aggressive papillary and chromophobe lesions. Clear cell RCCs and oncocytomas tended to be hypervascular, chromophobe lesions and angiomyolipomas tended to enhance moderately, and papillary lesions were mostly hypovascular. CONCLUSION: Certain imaging features and the degree of enhancement may be helpful in differentiating subtypes of renal cortical tumors.     

Spoke-wheel pattern in renal oncocytoma seen on double-phase helical CT

Renal oncocytomas are benign, solid tumours of the kidney. An angiographic spoke-wheel pattern is known to be associated with oncocytomas, although it is not pathognomonic. On review of the literature, we found two reports of sonographic spoke-wheel appearance in oncocytomas. These were sufficiently characteristic to enable a confident preoperative diagnosis of oncocytoma. We present a case of a surgically proven oncocytoma with a distinct helical CT appearance, -commensurate with the angiographic and sonographic spoke-wheel appearance from which the diagnosis was suspected preoperatively.     

[1-<Superscript>11</Superscript>C]Acetate uptake is not increased in renal cell carcinoma

Purpose The purpose of this study was to investigate the potential of [1-¹¹C]acetate (AC) as a metabolic tracer for renal cell cancer in human subjects. Methods Twenty-one patients with suspected kidney tumours were investigated with AC and dynamic PET. AC uptake was scored on a five-step scale. Tumour localisation was known from CT/MRI. Histology was available in 18/21 patients. The results in these 18 patients are reported. Results AC uptake by the tumour was less than (n = 11), equal to (n = 5) or higher than (n = 2) uptake in the surrounding renal parenchyma. Histological tumour types showed a typical distribution, with a predominance of clear cell carcinomas (n = 14) and only a small number of papillary cell carcinomas (n = 2) and oncocytomas (n = 2). Only the benign oncocytomas were highly positive with AC. Conclusion In most kidney tumours the AC accumulation was not higher than in normal kidney parenchyma. Therefore, AC PET cannot be recommend for the characterisation of a renal mass.     

Small renal Oncocytomas: Differentiation with multiphase CT

Objectives

To evaluate characteristic imaging findings of tumor attenuation in multiphase computed tomography (CT) between renal oncocytomas and clear-cell renal cell carcinoma (ccRCC) of small tumor size (≤5 cm).

Methods

We retrospectively identified 20 patients with complete four-phase CT with either histologically confirmed small renal oncocytoma (N = 10) or ccRCC (N = 10) who underwent subsequent total or partial nephrectomy. Exclusion criteria for RCC were non-clear-cell components in histology and a tumor diameter >5 cm. The relative attenuation of solid renal lesions and normal renal cortex was determined in the unenhanced, corticomedullary, nephrographic and excretory phase. Statistical comparison was carried out by Wilcoxon Rank Sum Test.

Results

Mean tumor size of renal oncocytomas was 2.8 ± 0.4 cm (1.2-5) and of ccRCC 2.5 ± 0.2 cm (1.7-4.4; p = 0.57). All lesions were homogenous without extended areas of necroses. In the nephrographic phase, the difference of attenuation between renal cortex and tumor lesion was highest in both entities (oncocytoma, 48.1 ± 5.2 HU; ccRCC, 67.5 ± 12.1) but not between entities (p = 0.30). In the corticomedullary phase, renal oncocytomas showed greater isodensity to the normal renal cortex (13.9 ± 4.3 HU) compared to clear-cell RCC (51.5 ± 5.0 HU; p = 0.003). No further significant differences were found for the unenhanced and excretory phase.

Conclusions

In this study, the maximum tumor-to-kidney contrast coincided with the nephrographic phase which was thus the most reliable for the detection of a renal lesion <5 cm. For lesion characterization, the corticomedullary phase was most useful for differentiating both entities. This finding is particularly important for the preoperative planning of a partial nephrectomy.     

Imaging of hereditary renal cancer

Over the past 5 years there have been dramatic developments in the extent of knowledge of hereditary renal cancers. In addition to VHL, which is associated with clear cell carcinoma, one can now list HPRC (associated with type I papillary renal cancer) and HLRCC (associated with type II papillary renal cancer). BHD and FRO are associated with chromophobe carcinoma and oncocytomas, although other histologic tumor types have been found in BHD. Medullary carcinoma of the kidney is associated with sickle cell trait. Although the genes associated with these tumors have been discovered, the exact mechanisms by which they cause renal cancer remain to be elucidated. It is quite likely that other genes also are involved in this process. Using VHL as an example, research is now underway on targeting mutant pVHL or excess HIF for diagnostic and therapeutic purposes. Understanding the mechanisms leading to cancer may open new targets of opportunity for drug development. This improved knowledge of the biogenetic pathways used to form tumors will impact the development of new therapeutic techniques for treating renal cancers in hereditary and nonhereditary forms of the disease.     

Fluid levels in aneurysmal bone cysts: a CT feature

The sonographic features of 15 histologically confirmed renal oncocytomas in 14 patients are presented. Lesions were evaluated for homogeneity, echogenicity, margination, venous invasion, and nodal enlargement. Nine were less than 5.5 cm in diameter, homogeneous, and well circumscribed. Three lesions were greater than 8 cm in diameter, contained areas of central necrosis or calcification, and were nonspecific for renal oncocytoma. One of these lesions (12 cm) contained a central scar. Two masses were slightly inhomogeneous and, at best, moderately circumscribed. In no case were metastatic nodes or venous invasion present. Since about 6% of renal cell carcinomas may have this appearance, the homogeneous, well marginated renal mass that is isoechoic with cortex and less than 5.5 cm in diameter is as likely to represent renal cell carcinoma as it is an oncocytoma. Although only present in one of the cases, the central fibrotic scar in a larger mass has been described in oncocytoma and may be the most specific feature. Preoperative investigation with fine-needle aspiration biopsy for cytology may be indicated in an attempt to avoid radical nephrectomy in selected patients.     

MSCT多期扫描对肾嗜酸细胞腺瘤与嫌色细胞癌的鉴别诊断价值

目的探讨多层螺旋CT(MSCT)四期扫描对肾嗜酸细胞腺瘤(renal oncocytoma,RO)与嫌色细胞癌(chro-mophobe cell renal carcinoma,CCRC)的鉴别诊断价值。资料与方法搜集经手术病理证实的8例(9个)RO和15例CCRC患者的资料,术前全部行CT平扫和三期增强扫描,采用SPSS 16.0软件对两种肿瘤的影像学表现进行统计学处理。结果病变平扫时密度值、钙化、强化的均匀性及中央星状瘢痕在RO组和CCRC组间的差异具有统计学意义(P<0.05);病变的大小、增强扫描各期的强化程度以及病变出现包膜、出血、坏死囊变、"辐轮"状强化及节段性增强反转等征象的比较,差异无显著性统计学意义(P>0.05)。结论 MSCT对术前RO和CCRC的鉴别诊断具有重要价值,平扫密度值、钙化、强化的均匀性及中央星状瘢痕有助于两者的鉴别。