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.     

Renal oncocytoma: new observations

Renal oncocytomas are uncommon, benign tumors that can be treated by local excision or heminephrectomy; their preoperative differentiation from renal cell carcinoma, treated by radical nephrectomy, would be invaluable. A particularly important finding, a central scar--not stressed in previous reports, is frequently demonstrated by CT examination. We evaluated radiographic studies of 18 pathologically confirmed cases of oncocytoma and compared findings with results of CT, sonography, and angiography studies of 18 renal cell carcinoma cases. Oncocytomas can be suggested if a stellate scar is identified within an otherwise homogenous tumor on ultrasound (US) and CT; if the mass appears homogeneous but no scar is present, angiography should be performed. An oncocytoma can be suggested in these cases if a spoke-wheel configuration and homogeneous blush are present. These criteria, which are reliable only if the mass is 3 cm or larger, would have resulted in the correct diagnosis of oncocytoma in 16/18 cases.     

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.     

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.     

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。     

Oncocytoma: the vanishing parotid mass

Parotid gland oncocytoma is an uncommon, benign salivary neoplasm composed of mitochondria-rich oncocytes. The purpose of this study was to correlate MR imaging and histopathology of parotid gland oncocytomas and to define the features that may distinguish these neoplasms from other benign and malignant parotid gland tumors. The MR imaging features in 9 patients with a pathologic diagnosis of oncocytoma were retrospectively reviewed. The imaging features were strikingly similar for 8 of the 9 patients. All lesions appeared T1 hypointense but isointense to the native parotid gland on fat-saturated T2 and postcontrast T1 imaging. On MR imaging, parotid gland oncocytomas share specific imaging characteristics that have not been described for benign or malignant parotid gland tumors. Oncocytomas are isointense to native parotid gland on fat-saturated T2 and T1 postcontrast MR images. Preoperative identification of correct histology may help surgical planning.     

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.     

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.     

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.     

Usefulness of multidetector computed tomography to differentiate between renal cell carcinoma and oncocytoma. A model validation

Objective:The purpose of this study is to validate a multivariable predictive model previously developed to differentiate between renal cell carcinoma (RCC) and oncocytoma using CT parameters.Methods and materials:We included 100 renal lesions with final diagnosis of RCC or oncocytoma studied before surgery with 4-phase multidetector CT (MDCT). We evaluated the characteristics of the tumors and the enhancement patterns at baseline, arterial, nephrographic and excretory MDCT phases.Results:Histopathologically 15 tumors were oncocytomas and 85 RCCs. RCCs were significantly larger (median 4.4 cm vs 2.8 cm, p = 0.006). There were significant differences in nodule attenuation in the excretory phase compared to baseline (median: 31 vs 42, p = 0.015), with RCCs having lower values. Heterogeneous enhancement patterns were also more frequent in RCCs (85.9% vs 60%, p = 0.027).Multivariable analysis showed that the independent predictors of malignancy were the enhancement pattern, with oncocytomas being more homogeneous in the nephrographic phase [Odds Ratio (OR) 0.16 (95% CI 0.03 to 0.75, p = 0.02)], nodule enhancement in the excretory phase compared to baseline, with RCCs showing lower enhancement [OR 0.96 (95% CI 0.93 to 0.99, p = 0.005)], and a size > 4 cm, with RCCs being larger [OR 5.89 (95% CI 1.10 to 31.58), p = 0.038].Conclusion:The multivariable predictive model previously developed which combines different MDCT parameters, including lesion size > 4 cm, lesion enhancement in the excretory phase compared to baseline and enhancement heterogeneity, can be successfully applied to distinguish RCC from oncocytoma.Advances in knowledge:This study confirms that multiparametric assessment using MDCT (including parameters such as size, homogeneity and enhancement differences between the excretory and the baseline phases) can help distinguish between RCCs and oncocytomas. While it is true that this multiparametric predictive model may not always correctly classify renal tumors such as RCC or oncocytoma, it can be used to determine which patients would benefit from pre-surgical biopsy to confirm that the tumor is in fact an oncocytoma, and thereby avoid unnecessary surgical treatments.     

Diagnostic accuracy of segmental enhancement inversion for the diagnosis of renal oncocytoma using biphasic computed tomography (CT) and multiphase contrast-enhanced magnetic resonance imaging (MRI)

Objectives

Segmental enhancement inversion (SEI) is a controversial imaging finding reportedly specific for the diagnosis of renal oncocytoma. The purpose of this study was to re-evaluate SEI using biphasic CT and multiphase MRI.

Methods

With research ethics board approval, a retrospective analysis of patients with resection or biopsy of oncocytoma or chromophobe renal cell carcinoma (Ch-RCC) between 2008-2012 was performed. Twenty-four patients with oncocytoma and 13 patients with Ch-RCC underwent CT, while 13 patients with oncocytoma and 10 patients with Ch-RCC underwent MRI. Two blinded radiologists reviewed the CT and MRI studies independently in separate sessions to assess for SEI. A third radiologist established consensus. Interobserver variability was calculated and diagnostic accuracy was compared using ROC and the Fisher exact test.

Results

There was no difference in detection of SEI between oncocytoma and Ch-RCC at CT [both readers (p?=?0.65, 0.5) and consensus review (p?=?0.29)] or MRI [both readers (p?=?0.64, 0.74) and consensus review (p?=?0.53)]. The interobserver variability at CT (K?=?0.28-0.33) and MRI (K?=?0.25-0.44) was fair. The sensitivity and specificity for diagnosis of oncocytoma were 21 % and 92 % at CT and 15 % and 90 % at MRI.

Conclusion

SEI is not useful for the diagnosis of renal oncocytoma with CT or MRI.

Key Points

? SEI was detected in a minority of renal oncocytomas and chromophobe RCC. ? Interobserver agreement for segmental enhancement inversion was only fair. ? SEI is not useful for diagnosing renal oncocytoma with CT or MRI.     

肾嗜酸细胞腺瘤的影像学表现及鉴别诊断

目的：探讨肾嗜酸性细胞腺瘤的CT和MRI表现,以提高对本病的认识。方法：回顾性分析经病理证实的9例肾嗜酸细胞腺瘤患者的影像资料。9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;其中1例同时行MRI检查,1例行IVP检查。结果：CT平扫示9例病灶均为单发;7例位于左肾,2例位于右肾,最大径2．0—10．0cm,平均5．1cm,〈3．0cm者2例,2例可见钙化。增强扫描：肾皮质期示9例病灶明显强化,肾髓质期示6例病灶持续强化,6例病灶内可见“星芒”状瘢痕,5例有相对完整假包膜。1例病灶于MRI T1WI上呈等、低信号,T2WI呈混杂高信号,可见清晰包膜。结论：肾嗜酸细胞腺瘤的影像学表现有一定特征性,有助于同肾癌和肾血管平滑肌脂肪瘤鉴别。     

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.     

Case report: characteristic ultrasonographic appearance of a large renal oncocytoma

The sonographic appearance of a large renal oncocytoma is described. The 'spoke-wheel' of hypoechoic radiating bands within the tumour was found to correlate closely with other imaging modalities and the histopathological appearance of the surgical specimen. This characteristic sonographic picture, which appears to be a feature of size, enabled a confident pre-operative diagnosis to be made.     

Retroperitoneal oncocytoma: case report and review of the imaging features

Oncocytomas are uncommon tumours that occur in a number of specific anatomical locations within the head, neck, chest, abdomen and pelvis. When occurring in the retroperitoneum, oncocytomas almost always arise from either the kidney or adrenal gland. With this case we present the imaging findings of an exceptionally rare retroperitoneal oncocytoma whose site of origin is neither the kidney nor adrenal gland.     

肝脏局灶性结节性增生超声造影的典型特征和病灶大小的相关性研究

目的:探讨肝脏局灶性结节性增生(FNH)超声造影的典型特征与病灶大小的联系。方法:本组采用新型超声对比剂SonoVue和对比脉冲序列成像技术,对33例FNH患者共35个病灶行超声造影检查(CEUS),观察病灶的增强模式和其它声像图特征,分析轮幅状的增强模式和中央疤痕的发生率;其中26例由CT、MRI证实,其余7例经手术或穿刺病理证实。结果:24个直径>3cm的病灶22个(22/24,91.7%)动脉相早期呈轮幅状增强,而11个直径<3cm的病灶4个(4/11,36.4%)为轮幅状增强,本组共计26个(26/35,74.3%)病灶呈轮幅状增强。本组22个(22/35,62.9%)病灶可见中央疤痕,其中19个(19/24,79.2%)直径>3cm的病灶和3个(3/11,27.3%)直径<3cm的病灶可见上述特征。结论:多数直径>3cm的FNH超声造影动脉相表现为典型的轮幅状增强模式,延迟相可见中央疤痕,如果无轮幅状增强和中央疤痕等声像图特征,则超声造影难以鉴别诊断FNH与其它富血供的肿瘤。     

Medullary CT enhancement in acute renal artery occlusion.

The diagnosis of traumatic renal artery occlusion by CT is based on finding the cortical rim sign, nonopacification of the pelvocalyceal system, and occasionally direct visualization of the thrombosed renal artery. We present four patients with renal artery occlusion who have an unusual pattern of medullary enhancement that has a vermiform and spoke-wheel appearance. It is important to realize that this enhancement does not represent functional renal tissue with a partially occluded renal artery. Instead, it is part of the spectrum of findings seen with complete occlusion of the renal artery.     

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。     

Scar sign of renal oncocytoma: Magnetic resonance imaging appearance and lack of specificity

This case report illustrates the magnetic resonance imaging (MRI) appearance of a typically asymptomatic renal oncocytoma as a homogeneous mass of medium signal with a stellate central region of decreased signal, representing the central scar. The MRI was correlated with computed tomography (CT), ultrasound (US), and gross pathologic appearance. The appearance of a central scar is not specific for oncocytoma and does not exclude renal cell carcinoma, as illustrated by a second case.     

The “mini brain” appearance of plasmacytoma in the appendicular skeleton

We report on the case of a 70-year-old woman presenting with right hip pain. Radiographs of the right hip demonstrated a well-defined large lytic lesion in the proximal right femur, with prominent trabeculae situated peripherally and extending into the lesion in a "spoke-wheel" pattern. Magnetic resonance imaging (MRI) demonstrated solid enhancing marrow-replacing lesion, with intervening linear nonenhancing areas of low T2 signal intensity. The MRI appearance resembled that of a small brain or "mini brain". Biopsy specimen demonstrated predominantly mature plasma cells, with occasional admixed immature forms. A diagnosis of plasmacytosis, consistent with myeloma, was made. This case illustrates a rare but seemingly characteristic "mini brain" appearance of plasmacytoma, which, to date, has only been reported in the spine and has not been observed in other bony lesions.