Changing concepts in the management of renal oncocytoma

Exploratory Analysis of the Role of Radiomic Features in the Differentiation of Oncocytoma and Chromophobe RCC in the Nephrographic CT Phase

In diagnostic imaging, distinguishing chromophobe renal cell carcinomas (chRCCs) from renal oncocytomas (ROs) is challenging, since they both present similar radiological characteristics. Radiomics has the potential to help in the differentiation between chRCCs and ROs by extracting quantitative imaging. This is a preliminary study of the role of radiomic features in the differentiation of chRCCs and ROs using machine learning models. In this retrospective work, 38 subjects were involved: 19 diagnosed with chRCCs and 19 with ROs. The CT nephrographic contrast phase was selected in each case. Three-dimensional segmentations of the lesions were performed and the radiomic features were extracted. To assess the reliability of the features, the intraclass correlation coefficient was calculated from the segmentations performed by three radiologists with different degrees of expertise. The selection of features was based on the criteria of excellent intraclass correlation coefficient (ICC), high correlation, and statistical significance. Three machine learning models were elaborated: support vector machine (SVM), random forest (RF), and logistic regression (LR). From 105 extracted features, 41 presented an excellent ICC and 6 were not highly correlated with each other. Only two features showed significant differences according to histological type and machine learning models were developed with them. LR was the better model, in particular, with an 83% precision.

A Giant Oncocytoma in an Elderly Female Patient: A Case Report

Renal oncocytomas are rare, benign tumors that can be difficult to distinguish from malignant renal cell carcinomas. This case report presents an 84-year-old woman with a sizeable renal oncocytoma and discusses this rare entity's diagnostic challenges and management.

Asymptomatic Giant Right Renal Oncocytoma: A Case Report

Renal oncocytoma is usually detected incidentally. It can be considered as a renal cell carcinoma (RCC) on preoperative imaging. They usually present as small masses and usually look like benign tumors. Giant oncocytomas are rare. A 72-year-old male patient was seen in the outpatient department for left scrotal swelling. Ultrasound (US) showed a giant mass compatible with RCC in the right kidney which was incidentally detected. Abdominal computed tomography (CT) revealed a mass with an axial diameter of 167×146 mm, compatible with RCC, a heterogeneous mass of soft tissue density with central necrosis. There was no evidence of tumor thrombus in the right renal vein or inferior vena cava. Open radical nephrectomy was performed through an anterior subcostal incision. Pathological examination revealed a 17×15 cm renal oncocytoma. The patient was discharged on the sixth day postoperatively. Clinically or radiologically, renal oncocytoma and renal cell carcinoma usually cannot be distinguished, although oncocytoma may be suspected if a central scar with fibrous extensions is seen, the so-called "spoke-wheel appearance". The treatment decision should be made according to the clinical aspects. Radical/partial nephrectomy or thermal ablation can be considered as treatment options. In this article, we review the literature on the radiological and pathological features of renal oncocytoma.

Bilateral Renal Oncocytoma: Active Surveillance Versus Partial Nephrectomy

Renal oncocytomas (ROs) are benign tumors comprising 16% of renal masses. Due to the overlapping phenotypes seen in RO and chromophobe renal cell carcinoma (RCC) and lack of specific clinical and laboratory characteristics of RO, physicians face a challenge when arriving at a definitive diagnosis of RO. ROs additionally appear indistinct from RCCs on CT scan, contributing further to the difficulty of arriving at a clear diagnosis of RO. 

This is a case report of a 66-year-old man who presented with flank pain found to be related to bilateral ROs and underwent bilateral partial nephrectomies.

ROs are benign small renal masses that often pose a diagnostic challenge since preoperative diagnosis can be difficult to achieve. Given advancements in technology, active surveillance with core renal biopsy is a promising approach to accurately diagnose and manage ROs conservatively. The application of these techniques has wide-reaching implications for patients and physicians by reducing the need for a potentially harmful surgery and creating a cost-effective way to manage a diagnosis.

Ultrasonography findings for the diagnosis of renal oncocytoma

Renal oncocytomas are rare benign epithelial tumors of the kidney. However, they are easily misdiagnosed as renal cancers, resulting in unnecessary radical nephrectomy. This review summarizes the use of ultrasound for the diagnosis of renal oncocytomas. On two-dimensional grayscale ultrasound, renal oncocytomas appear as solid, well-defined, round or oval, and relatively isoechoic or slightly hyperechoic masses. On color Doppler flow imaging, the "spoke-wheel" sign is evident. On power Doppler flow imaging, renal oncocytomas show mixed penetrating and peripheral patterns. Renal oncocytomas usually appear as highly enhanced on contrast-enhanced ultrasound images, and irregular nonenhanced areas in larger tumors. This review will help sonographers recognize renal oncocytomas.

Oncocytoma-Related Gene Signature to Differentiate Chromophobe Renal Cancer and Oncocytoma Using Machine Learning

Publicly available gene expression datasets were analyzed to develop a chromophobe and oncocytoma related gene signature (COGS) to distinguish chRCC from RO. The datasets GSE11151, GSE19982, GSE2109, GSE8271 and GSE11024 were combined into a discovery dataset. The transcriptomic differences were identified with unsupervised learning in the discovery dataset (97.8% accuracy) with density based UMAP (DBU). The top 30 genes were identified by univariate gene expression analysis and ROC analysis, to create a gene signature called COGS. COGS, combined with DBU, was able to differentiate chRCC from RO in the discovery dataset with an accuracy of 97.8%. The classification accuracy of COGS was validated in an independent meta-dataset consisting of TCGA-KICH and GSE12090, where COGS could differentiate chRCC from RO with 100% accuracy. The differentially expressed genes were involved in carbohydrate metabolism, transcriptomic regulation by TP53, beta-catenin-dependent Wnt signaling, and cytokine (IL-4 and IL-13) signaling highly active in cancer cells. Using multiple datasets and machine learning, we constructed and validated COGS as a tool that can differentiate chRCC from RO and complement histology in routine clinical practice to distinguish these two tumors.

Solid renal masses in adults

With the ever increasing trend of using cross-section imaging in today's era, incidental detection of small solid renal masses has dramatically multiplied. Coincidentally, the number of asymptomatic benign lesions being detected has also increased. The role of radiologists is not only to identify these lesions, but also go a one step further and accurately characterize various renal masses. Earlier detection of small renal cell carcinomas means identifying at the initial stage which has an impact on prognosis, patient management and healthcare costs. In this review article we share our experience with the typical and atypical solid renal masses encountered in adults in routine daily practice.

Imaging Characterization of Renal Masses

The detection of a renal mass is a relatively frequent occurrence in the daily practice of any Radiology Department. The diagnostic approaches depend on whether the lesion is cystic or solid. Cystic lesions can be managed using the Bosniak classification, while management of solid lesions depends on whether the lesion is well-defined or infiltrative. The approach to well-defined lesions focuses mainly on the differentiation between renal cancer and benign tumors such as angiomyolipoma (AML) and oncocytoma. Differential diagnosis of infiltrative lesions is wider, including primary and secondary malignancies and inflammatory disease, and knowledge of the patient history is essential. Radiologists may establish a possible differential diagnosis based on the imaging features of the renal masses and the clinical history. The aim of this review is to present the contribution of the different imaging techniques and image guided biopsies in the diagnostic management of cystic and solid renal lesions.

Synchronous sporadic bilateral multiple chromophobe renal cell carcinoma accompanied by a clear cell carcinoma and a cyst: A case report

BACKGROUND

Renal cell carcinomas are usually unilateral. However, they are bilateral in 2% to 4% of sporadic cases and is considerably more common in familial cases. Synchronous sporadic bilateral multiple chromophobe renal cell carcinoma (CHRCC) with different subtypes is rare.

CASE SUMMARY

In this case report, we describe a case of synchronous bilateral CHRCC with two histological variants, accompanied by a clear cell carcinoma and a cyst in a 50-year-old male. The patient underwent retroperitoneal laparoscopic bilateral nephron-sparing surgery and there was no serious postoperative renal dysfunction.

CONCLUSION

We report a rare case of synchronous bilateral CHRCC with two histological variants associated with a clear cell carcinoma and a cyst.

A Case of Renal Oncocytoma with Renal Venous Tumor Thrombus

Renal oncocytoma is generally regarded as a benign renal tumor. We herein report a case of large renal oncocytoma with renal venous tumor thrombus. The patient may need to be carefully followed up because hematogenous metastasis may occur.

Thyroid and renal tumors in patients treated with long-term lithium: case series from a lithium clinic, review of the literature and international pharmacovigilance reports

BACKGROUND

Cancer had never been considered as a relevant problem in patients treated with lithium until 2015, when a document published by the European Medicine Agency concluded that long-term use of lithium might induce renal tumors. A few months later, we observed the case of a woman treated with lithium for 18 years who was diagnosed with both thyroid and renal tumors.

METHODS

This study aimed to investigate the correlation between lithium treatment and thyroid or renal tumors. We analyzed clinical records in our lithium clinic database, causes of death of patients who had been visited at least once at the lithium clinic, reports of lithium adverse reactions in the European and WHO pharmacovigilance databases, and published cases of thyroid and renal tumors in long-term lithium-treated patients.

RESULTS

Of the 1871 lithium patients who had been visited at least once between 1980 and 2013, eight had been diagnosed with thyroid papillary carcinoma and two with clear-cell renal-cell carcinoma. No cases of thyroid cancer and only one case of renal tumor were the cause of death according to the 375 available death certificates. VigiAccess database contained a total of 29 and 14 cases of renal and thyroid tumors, respectively. EudraVigilance database contained 21 cases of renal and 8 of thyroid neoplasms. Literature search yielded 6 published cases of thyroid papillary carcinoma and 25 cases of various renal tumors. However, two population-based studies did not find any increased risks of cancer in patients exposed to lithium, whereas two nationwide studies did not find any excess of renal tumors.

CONCLUSION

So far it has not been possible epidemiologically to confirm an increased risk of thyroid or renal cancers associated with lithium. Such a conclusion is supported by the findings of low rates and mortalities of thyroid or renal cancers from the present lithium clinic data.

Oncocytoma managed by active surveillance in a transplant allograft kidney: a case report

BACKGROUND

The ethical implications of the utilization of kidneys with solid renal masses (SRMs) in transplantation are the subject of lively debate in the transplantation community and beyond. One of such implications is that as the life expectancy of renal transplant patients improve, the prevalence of SRMs in donors is likely to increase. We report a case of an oncocytoma in a renal allograft complicating a deceased-donor kidney transplant.

CASE PRESENTATION

A 60-year-old woman received and underwent deceased-donor renal transplantation for end-stage renal disease after a waiting-list period of 11 years. Kidney Doppler ultrasound (DUS) of the deceased donor was negative for any nodular lesion. The finding of the DUS, done on postoperative day 1, to assess the patency of the graft, was suspicious for an acute arterial thrombosis but did not reveal any focal irregularities. An ensuing computed tomography (CT) scan did not show any arterial complications but serendipitously revealed a 2.4-cm lesion on the upper pole of the renal allograft, which was not detected during the back-table or ultrasonography monitoring. Histology of the biopsied lesion was consistent with oncocytoma. However, because the eosinophilic variant of chromophobe renal cell carcinoma may morphologically resemble renal oncocytoma, immunohistochemical staining was performed. The results were negative, ruling out chromophobe RCC. After discussing the therapeutic options and potential related outcomes with the patient, we found no reason for resection of the lesion or an allograft nephrectomy, given the low risk of malignant transformation in an oncocytoma. Active surveillance of the benign tumor was done with ultrasonography, every 2 months, for the first year and, then, with magnetic resonance imaging, every year. The patient received mycophenolate-mofetil, tacrolimus, and prednisone throughout the 5-year follow-up period, and the regimen for immunosuppression was not changed despite the presence of the renal mass. After 60 months, we report that none of the radiological findings have shown any morphological changes of the lesion, and the patient is well.

CONCLUSION

To the best of our knowledge, we report the first case of an oncocytoma in a renal allograft complicating a deceased-donor kidney transplant, which was successfully managed by active surveillance.

A Rare Benign Tumor in a 14-Year-Old Girl

Background

Oncocytomas are the second most common benign renal neoplasm but, unfortunately, they are difficult to differentiate from renal cell carcinoma. Renal oncocytomas are rare and have mostly been reported in adults. To our knowledge, this is only the sixth pediatric reported case of renal oncocytoma worldwide.

Case Presentation

A 14-year-old Yemeni girl with a recurrent history of urinary tract infections came to our clinic complaining of left flank pain with a frontal headache. Ultrasound showed a 3 cm, well-defined echogenic lesion with mild vascularity. This lesion increased in size on her subsequent follow-ups. Computed tomography showed no intralesional fat, vessels invasion, or enlarged lymph nodes. The patient underwent laparoscopic radical nephrectomy, and a pathology report confirmed the diagnosis of renal oncocytoma.

Conclusion and Recommendations

We present the rare occurrence of renal oncocytoma in a pediatric patient and highlight the importance of considering oncocytomas in the diagnosis of a renal mass.

Dilemmas in diagnosis and natural history of renal oncocytoma and implications for management

INTRODUCTION

Oncocytomas have traditionally been treated with surgical excision; however, their excellent long-term prognosis has popularized conservative and minimally invasive ablative techniques. We evaluated the evolving management and natural history of renal oncocytomas and investigated the relationship between radiological and histopathological diagnosis.

METHODS

We performed a 17-year retrospective cohort study on all patients with a confirmed histopathological diagnosis of renal oncocytoma. The primary outcome variables were long-term outcomes, coexistence with renal cell carcinoma, and development of metastatic disease.

RESULTS

A total of 38 oncocytomas were reported in 36 patients. Of the 36 patients, 29 (81%) were diagnosed incidentally. Oncocytoma was considered in the differential diagnosis in 4 oncocytomas (10.5%). In total, 34 patients underwent early surgical intervention; of these, 27 (79.4%) underwent radical nephrectomy and 7 underwent partial nephrectomy (20.6%). Four patients (11.1%) were managed conservatively with surveillance. No patients developed recurrence or metastatic disease after a median follow-up of 84 months (range: 4-178).

CONCLUSIONS

The diagnostic accuracy for imaging modalities in renal oncocytoma is poor. Surveillance or minimally invasive ablative techniques are appropriate in selected patients with biopsy-proven oncocytoma that are not increasing in size.

Solid renal tumours of collecting duct origin in patients on chronic lithium therapy

Background

Lithium (Li) is an invaluable drug for the treatment of bipolar disorder. Long-term Li use is associated with renal complications including the formation of uncomplicated renal cysts caused by proliferation and expansion of collecting duct (CD) cells. We report six patients with complicated renal cysts in the context of Li nephropathy.

Methods

Over a time period of 15 years, we have identified six patients with one or more solid renal tumours in our population of approximately 50 patients with chronic Li nephropathy. In this study we describe the clinical and pathological characteristics of these Li-related tumours.

Results

All patients were on Li therapy for over 10 years and suffered from varying degrees of Li nephropathy. The tumours were all of CD origin and comprised both oncocytomas and collecting duct carcinomas. The CD carcinomas differed from the very rare “classical” CD cell carcinomas in histological appearance, multifocal presentation and non-aggressive clinical behaviour

Conclusions

The increased incidence of CD derived tumours and atypical presentation of CD cell carcinomas in patients with chronic Li nephropathy suggests that Li predisposes to the development of these tumours. We hypothesize that prolonged stimulation of CD cell proliferation and expansion by Li not only causes cyst formation, but can eventually induce the formation of adenomas and carcinomas. Increased awareness of a possible relationship between chronic Li therapy and renal neoplasms, will enhance the knowledge on epidemiology, clinical behavior and optimal therapy for the Li-related renal neoplasms.

Imaging spectrum of renal oncocytomas: a pictorial review with pathologic correlation

OBJECTIVES

The purpose of this pictorial review is to present the imaging spectrum of renal oncocytomas with radiological-pathological correlation.

CONCLUSION

The differences in tumour cellularity (high cellularity or low cellularity with abundant stroma) and haemorrhagic/cystic change contribute to a wide spectrum of imaging findings of renal oncocytomas. Imaging findings substantially overlap those of common subtypes of clear cell and non-clear cell renal cell carcinomas. Multifocal renal oncocytomas are not rare, and making the diagnosis of oncocytoma with concomitant renal cell carcinoma is difficult. In addition, renal oncocytomas that demonstrate interval growth or develop in the setting of end-stage renal disease may be mistaken for malignancy.

TEACHING POINTS

• High cellular components demonstrate avid arterial enhancement and subsequent washout. • Low cellular components demonstrate gradual subsequent enhancement owing to abundant stroma. • Cystic and hemorrhagic changes may account for lesion heterogeneity in the delayed phase. • Multifocal oncocytomas and oncocytomas coexisting with renal cell carcinoma are not rare. • Renal oncocytomas may demonstrate interval growth.

Characterization of renal cell carcinoma, oncocytoma, and lipid-poor angiomyolipoma by unenhanced, nephrographic, and delayed phase contrast-enhanced computed tomography

The purpose of this study was to assess the characterization of renal cell carcinoma (RCC) and benign renal tumors by unenhanced, nephrographic, and delayed phase computed tomography (CT). The study group consisted of 129 renal tumors including 79 clear cell RCCs, 17 papillary RCCs, 6 chromophobe RCCs, 21 oncocytoma, and 6 lipid-poor angiomyolipomas (AMLs). CT studies were retrospectively reviewed. Our results suggested that it was possible to discriminate clear cell RCC from papillary RCC, chromophobe RCC, and lipid-poor AML. CT findings of oncocytoma overlapped with both clear cell and non-clear cell RCCs, although oncocytoma more commonly became homogeneous in the delayed phase.

Comparison of segmental enhancement inversion on biphasic MDCT between small renal oncocytomas and chromophobe renal cell carcinomas

OBJECTIVE

The purpose of this article is to assess the usefulness of segmental enhancement inversion on biphasic MDCT in differentiating small (<4 cm) renal oncocytomas from chromophobe renal cell carcinomas (CRCCs).

MATERIALS AND METHODS

Eighty-two patients (40 men and 42 women) with a mean (±SD) age of 54±12 years (range, 21-75 years) with 27 renal oncocytomas and 55 CRCCs diagnosed by surgery who underwent contrast-enhanced biphasic CT between January 2000 and December 2011 were included. CT scans were interpreted by two radiologists who were blinded to the pathologic findings. The tumors were evaluated for size and segmental enhancement inversion. After independent evaluation, a consensus was reached by measuring the attenuation. Pathologic analysis determined the presence of fibrous septa, cystic change, hemorrhage, and necrosis. The Fisher exact test was used to evaluate the relationship between segmental enhancement inversion, tumor type, and specific pathologic changes. Interobserver concordance was evaluated with kappa statistics.

RESULTS

There were no significant differences in size between renal oncocytomas and CRCCs (p=0.458). Segmental enhancement inversion was present in 23, 20, and 21 (25.6%) of the 82 tumors according to reader 1, reader 2, and the consensus, respectively. The agreement was almost perfect (κ=0.843; p<0.001). Segmental enhancement inversion was more common in renal oncocytomas (63% [17/27]) than in CRCCs (7.3% [4/55]; p<0.001). There were no significant relationships between the four pathologic changes and tumor type or segmental enhancement inversion (p=0.351 and p=0.126, respectively).

CONCLUSION

Our study findings suggest that segmental enhancement inversion on biphasic MDCT may be useful in differentiating small renal oncocytomas from CRCCs.

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) mm(2)/s vs 2.10 ± 0.09 × 10(-3) mm(2)/s; P < 0.0001). Uroepithelial malignancies can be differentiated by lowest ADC values (1.30 ± 0.11 × 10(-3) mm(2)/s). There is a significant difference between ADC values of renal cell carcinomas and oncocytomas (1.61 ± 0.08 × 10(-3) mm(2)/s vs 2.00 ± 0.08 × 10(-3) mm(2)/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.

Multiple bilateral oncocytomas of the native kidneys following renal transplantation: report of a rare case and review of the literature

Renal oncocytomas are benign tumors of the kidneys, which are usually diagnosed postoperatively, due to differential diagnostic problems, from a sample of a renal cell carcinoma. The development of a renal oncocytoma in the native kidneys following renal transplantation is a very rare condition and only a few cases have been published in the world literature. In this case report we present a unique case of bilateral multifocal renal oncocytomas of the native kidneys in a female transplant recipient 6 years after renal transplantation. The patient’s postoperative clinical course was uneventful and no local recurrence or distant metastasis has been found so far. The pathology, clinical characteristics, and treatment of renal oncocytomas are also reviewed.

Combined late gadolinium-enhanced and double-echo chemical-shift MRI help to differentiate renal oncocytomas with high central T2 signal intensity from renal cell carcinomas

OBJECTIVE

The purpose of our study was to evaluate the combination of dynamic contrast-enhanced T1-weighted and double-echo gradient-echo MR imaging to distinguish renal oncocytoma with high T2 signal intensity centrally from renal cell carcinoma (RCC).

MATERIALS AND METHODS

Between 2006 and 2011, 63 renal tumors (59 patients) presenting with a high signal intensity (SI) central area on T2-weighted sequences were imaged with dynamic contrast-enhanced sequences, including phases later than 5 minutes after contrast injection, and double-echo chemical-shift sequences were selected from our institutional database. Two experienced radiologists visually assessed presence and distribution of signal enhancement of central areas after injection and measured SI changes on opposed-phase images for calculation of the SI index and tumor-to-spleen ratio. Cutoff values were derived from the receiver operating characteristic (ROC) curve.

RESULTS

There were 19 oncocytomas (16 patients), 43 RCCs (42 patients), and one leiomyoma. Complete late enhancement of the central area was observed in 14 oncocytomas (74%) and in five RCCs (12%) (p = 0.05). The combination of complete enhancement and SI index lower than 2% (p = 0.02) or tumor-to-spleen ratio higher than -6% (p = 0.001) provided sensitivity of 36% and 55%, specificity of 95% and 97%, positive predictive value of 67% and 86%, and negative predictive value of 84% and 88%, respectively, for diagnosis of oncocytomas.

CONCLUSION

Absence of central area SI inversion or presence of a signal drop on chemical-shift imaging may rule out the diagnosis of oncocytoma.

Renal oncocytoma: contrast-enhanced sonographic features

OBJECTIVES

The purpose of this study was to illustrate the features of renal oncocytoma on contrast-enhanced sonography.

METHODS

Five cases of surgical pathologically proven renal oncocytoma were retrospectively reviewed and analyzed in this study. The 5 patients studied included 3 men and 2 women with a mean age of 52.3 years (range, 32-66 years). All patients underwent conventional and contrast-enhanced sonographic examinations before surgery. The sonographic features, enhancement pattern, and dynamic perfusion change of the tumors and renal parenchyma in vascular phases were evaluated and compared to computed tomography.

RESULTS

On grayscale sonography, renal oncocytomas appeared as solitary hypoechoic or isoechoic masses originating from the renal cortex measuring 2 to 6 cm with a well-defined margin. Color Doppler flow imaging showed rich blood flow signals in the periphery and striplike blood flow signals within the masses. On contrast-enhanced sonography, the features of these tumors included early enhancement, hyperenhancement, and fast wash-out compared to the adjacent renal cortex. There were irregular nonenhanced areas seen in the center of the masses (n = 3) and nonenhanced thin rims seen in the periphery (n = 5). Macroscopically, the well-marginated tumors were yellowish brown with a tender texture and were located in the renal cortex. Central irregularly shaped fibrous scars were seen in 3 tumors, consistent with nonenhanced areas on contrast-enhanced imaging.

CONCLUSIONS

Contrast-enhanced sonography can provide valuable hemodynamic information on renal oncocytoma, which may help in making a differential diagnosis of this benign renal tumor in clinical practice.

[Renal oncocytoma in pregnancy--an unusual presentation of secondary hypertension]

INTRODUCTION

Renal oncocytoma accounts for 5-7% of primary renal neoplasms. It is usually, diagnosed in asymptomatic patients and is characterized by a benign behavior without invasion of adjacent tissues or metastasis. Diagnosis during pregnancy is uncommon and to date there have been only a few cases reported in the literature.

CASE REPORT

The authors present the case of a 32-year-old nulliparous woman with uncontrolled hypertension diagnosed at seven weeks gestation. She was referred to our institution at 24 weeks with superimposed pre-eclampsia complicated by acute pulmonary edema and hemodynamic instability requiring mechanical ventilatory support, fetal growth restriction and stillbirth. Etiological study of the hypertensive disorder performed in the postpartum period was consistent with renal oncocytoma.

CONCLUSION

The clinical behavior of renal oncocytoma remains poorly characterized during pregnancy and may lead to an adverse maternal and fetal outcome despite its theoretically benign behavior. It is essential to exclude a possible secondary cause of hypertension in cases that are difficult to control.

Synchronous colonic adenocarcinoma and renal oncocytoma: a case report and literature review

We present the case of a patient with an adenocarcinoma of the colon associated with an oncocytoma of the kidney. A left colonic cancer was diagnosed at colonoscopy and an incidental finding of a left renal mass was noted, with a staging computerized tomography scan. Following a left hemicolectomy and a left nephrectomy, the pathological report confirmed the presence of a colonic adenocarcinoma and revealed that the left renal mass was an oncocytoma. This case report reviews the management decisions associated with incidental renal masses as well as the treatment of synchronous neoplasia.

Successful one stage operation for a synchronous, duodenal carcinoma, colonic carcinoma and renal oncocytoma in an adult patient

We report a rare case of synchronous duodenal carcinoma, colonic carcinoma and renal oncocytoma successfully treated using a one-stage surgical approach. Potential risk factors for multiple primary malignancies associated with duodenal carcinoma are discussed. This case illustrates several practice points for consideration: 1. Patients presenting with small intestinal carcinomas have a higher than average chance of developing second primary tumors in other organs; this should be taken into consideration during staging and follow-up. 2. For full staging of patients presenting with small bowel tumors, upper and lower gastrointestinal endoscopy and PET scanning should be considered. 3. A one-stage surgical procedure can be used safely and successfully for multiple synchronous primary tumors.

Radiofrequency ablation of multifocal bilateral renal oncocytomas

Renal oncocytoma is a usually benign, typically solitary renal tumor, which cannot be reliably distinguished from other renal neoplasms on the basis of its imaging characteristics. Multifocality and/or bilaterality are very rare; to our knowledge only one case of multiple and/or bilateral oncocytomas is reported in the literature and was treated with partial nephrectomy. We report a case of a 72-year-old patient with multifocal and bilateral renal oncocytomas that were treated with radiofrequency ablation.

MRI features of renal oncocytoma and chromophobe renal cell carcinoma

OBJECTIVE

The purpose of this study was to retrospectively describe the MRI features of the pathologically related entities renal oncocytoma and chromophobe renal cell carcinoma (RCC).

MATERIALS AND METHODS

Twenty-eight cases of histologically proven renal oncocytoma and 15 of chromophobe RCC evaluated with preoperative MRI from January 2003 through June 2009 at our institution were independently reviewed for an array of MRI features by two radiologists blinded to the final histopathologic diagnosis. These features were tabulated and compared between chromophobe RCC and renal oncocytoma by use of the Mann-Whitney test and binary logistic regression.

RESULTS

Renal oncocytoma and chromophobe RCC showed no significant difference in size or any of 16 qualitative imaging features (p = 0.0842-1.0, reader 1; p = 0.0611-1.0, reader 2). Microscopic fat, hemorrhage, cysts, infiltrative margins, perinephric fat invasion, renal vein invasion, enhancement homogeneity, and hypervascularity were each observed in less than 20% of cases by both readers. A central scar and segmental enhancement inversion (a recently described finding in which early contrast-enhanced images show relatively more enhanced and less enhanced intralesional components with inversion of their relative enhancement on later images) were observed by both readers in at least 10% of cases of both renal oncocytoma and of chromophobe RCC with no significant difference between the two entities (p = 0.2092-0.2960).

CONCLUSION

We have presented the largest series to date of the MRI features of both renal oncocytoma and chromophobe RCC. These related entities exhibited similar findings, and no MRI features were reliable in distinguishing between them.

Incidental giant renal oncocytoma: a case report

Introduction

Large renal oncocytomas are not very rare entities. To the best of our knowledge, we report one of the largest oncocytomas in the English literature. The tumor was incidentally diagnosed and, based on the preoperative clinical and radiographic findings, was therefore considered to be a renal cell carcinoma.

Case presentation

A 48-year-old Caucasian diabetic man had an abdominal ultrasound for chronic abdominal discomfort, which revealed a large mass on the left kidney. An abdominal computed tomography scan revealed a contrast enhancing, well defined, heterogenous large mass (16.5 × 13.9 cm) originating from the left lower pole with cystic and solid areas. A magnetic resonance imaging scan was performed with no evidence of renal vein or caval thrombus or embolus. A radical nephrectomy was performed through a left flank intercostal incision and the pathology diagnosed renal oncocytoma. The postoperative course was uneventful and the patient was discharged six days later.

Conclusion

Several reports have characterised this essentially benign renal histiotype, which represents 5% to 7% of all solid renal masses. Unfortunately, most renal oncocytomas cannot be differentiated from malignant renal cell carcinomas by clinical or radiographic criteria. Central stellate scar and a spoke-wheel pattern of feeding arteries are unreliable diagnostic signs and are of poor predictive value. These tumors are treated operatively with radical or partial nephrectomy or thermal ablation, depending on the clinical circumstances. We report on, to the best of our knowledge, the fourth largest lesion of this type of renal pathology.

Chromophobe Renal Cell Carcinoma with Sarcomatoid Transformation in a Dog

A 12-year-old spayed female Siberian husky dog presented with hematuria and weight loss. An abdominal ultrasonographic examination revealed a left renal tumor measuring 8 cm in diameter, and a nephrectomy was performed. The resected kidney contained a cavitated tumor with a white solid region. Histologically, this tumor was composed of large polygonal cells with abundant and cloudy cytoplasm and focal sarcomatoid change. The neoplastic epithelial cells were reactive with colloidal iron staining; Dolichos biflorus agglutinin, peanut agglutinin, and Ulex europaeus agglutinin I lectins; and cluster of differentiation 10 and c-KIT antigens but not for periodic acid-Schiff or vimentin stain. Neoplastic sarcomatoid cells stained positive for vimentin. Because these histopathologic features are identical to those of human chromophobe renal cell carcinoma, the present case was diagnosed as canine chromophobe renal cell carcinoma.

Renal mass sampling: an enlightened perspective

Renal mass sampling (RMS) can be carried out by core biopsy or fine needle aspiration with each presenting potential advantages and limitations. The literature about RMS is confounded by a lack of standardized techniques, ambiguous terminology, imprecise definitions of accuracy, substantial rates of non-informative biopsies, and recurrent diagnostic challenges with respect to eosinophilic neoplasms. Despite these concerns, RMS has an expanding role in the evaluation and treatment of renal masses, in order to stratify biological aggressiveness and guide management that can range from surgery to active surveillance. Non-informative biopsies can be managed with surgical excision or repeat biopsy, with the latter showing encouraging results in recent studies. We propose a new classification in which all biopsies are categorized as non-informative versus informative, with the latter being subclassified as confirmed accurate, presumed accurate or confirmed inaccurate. This terminology will facilitate the comparison of results from various studies and stimulate progress. Incorporation of novel biomarkers and molecular fingerprinting into RMS protocols will likely allow for more rational management of patients with renal masses in the near future.

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.

Giant renal oncocytoma: a case report and review of the literature

INTRODUCTION

Renal oncocytomas are benign neoplasms derived from cells of the distal renal tubule, and comprise 5% to 7% of primary renal neoplasms. Oncocytomas are mostly asymptomatic, and the majority of tumors are discovered incidentally. In this case report, we present a case of a patient with a giant oncocytoma arising from her left kidney.

CASE PRESENTATION

We describe a 25-year-old Turkish woman who was admitted to our hospital with abdominal pain and a 3-year palpable abdominal mass, which was found present since her second pregnancy. Examination revealed a 15 x 20-cm mass in her abdominal cavity. Computed tomography revealed a mass with regular outlines, measuring 18 x 11 x 12 cm, associated with the left kidney, and causing marked hydroureteronephrosis. We excised the mass and performed a left nephrectomy on our patient. The immunohistopathology of the mass was consistent with renal oncocytoma. No local or distant metastasis was seen at 6 months postoperatively.

CONCLUSION

To the best of our knowledge, this is the second largest renal oncocytoma described in the English language literature. This is also the first reported giant oncocytoma that presented during pregnancy.

Can renal oncocytoma be distinguished from chromophobe renal cell carcinoma by the presence of fibrous capsule?

The most important differential diagnosis of chromophobe renal cell carcinoma (CRCC) is renal oncocytoma. Due to overlapping morphological characteristics of renal oncocytoma and CRCC, particularly its eosinophilic variant, making a correct diagnosis can be challenging. To date, no data are available on the presence of the tumor fibrous capsule as a diagnostic feature in differentiating these tumors. The main purpose of this study was to establish the presence and compare the thickness of the tumor fibrous capsule between two tumor groups. A total of 37 tumors--18 cases of CRCC (three eosinophilic and 15 classic) and 19 cases of renal oncocytoma--were analyzed. Four slides of each tumor stained with hematoxylin and eosin were first scanned at low-power magnification (x40) to assess the presence of the capsule. If present, the capsule was measured in three different thickest areas at higher magnification (x200). The mean value of capsule thickness was calculated and taken into consideration. The capsule was present in 12 (66.7%) cases of CRCCs and in only two (10.5%) cases of renal oncocytomas. Statistical analysis showed significant difference between the presence of fibrous capsule in these two observed tumor groups (P = 0.001). Average thickness of capsule in CRCCs was 337.7 microm, and 115.4 microm in renal oncocytomas, but the median was not statistically significant (P = 0.198). Studies with a larger number of cases are needed to conclude if this characteristic could be a low-cost, reliable microscopic feature in differentiating between CRCC and renal oncocytoma.

Unilateral simultaneous renal oncocytoma and angiomyolipoma: case report

A rare case of synchronous angiomyolipoma and oncocytoma in the same kidney of a 70 year old man is presented. A left renal mass was found incidentally by ultrasound. Computerized tomography and magnetic resonance imaging revealed a 1,3 cm mass in the mid-portion of the left kidney, whereas on the lower pole of the same kidney, a 3,3 cm mass was also revealed, consistent with angiomyolipoma. A working diagnosis of renal cell carcinoma was made. A radical nephrectomy was performed. Microscopically, the tumor of the lower pole was found to be an angiomyolipoma, whereas the mid-portion tumor was an oncocytoma. Until now, only 16 cases of unilateral simultaneous presence of renal angiomyolipoma and oncocytoma have been reported. Of these cases, all except one were female and three were associated with the tuberous sclerosis complex. It is well worth remarking, that renal oncocytoma overlap with other renal neoplasms, therefore nephrectomy remains the treatment of choice.Renal angiomyolipoma and oncocytoma are uncommon neoplasms and their simultaneous presence in the same kidney is rare. Only 16 cases have been reported until now in the literature. The purpose of this paper is to present an additional case without evidence of tuberous sclerosis.

Imaging and management of the incidentally discovered renal mass

Improvements in imaging technology and the expanding use of imaging have led to a rapid increase in the discovery of incidental renal lesions. These can present both the radiologist and the referring clinician with diagnostic dilemmas. This article addresses the most frequently encountered lesions and provides a framework for the diagnostic and management pathways for both solid and cystic lesions.

Renal Oncocytoma in Taiwan

BACKGROUND

Renal oncocytoma has been repeatedly reported in Western countries, but only a few cases have been reported in Eastern countries. This study aims to review the clinical course of renal oncocytoma in an Eastern country such as Taiwan.

MATERIALS AND METHODS

Sixteen cases of renal oncocytoma seen between 1987 and 2002 at Chang Gung Memorial Hospital, Taipei, Taiwan, were studied.

RESULTS

Preoperatively, all patients were diagnosed to have renal cell carcinoma, following various radiologic studies. Perioperatively, frozen sections of three patients indicated renal oncocytoma in two and renal cell carcinoma in one. Renal oncocytoma has marked similarities to renal cell carcinoma, according to various radiologic, cytologic, and pathological investigations, so an accurate diagnosis is difficult to achieve, either preoperatively or perioperatively. Therefore, rather than being treated with partial nephrectomy, all patients were treated aggressively with unilateral radical nephrectomy. Postoperatively, all 16 patients were followed up, from 12 to 189 months, with a mean of 58.7 months. Notably, all patients survived with no evidence of tumor recurrence.

CONCLUSIONS

The experience in Taiwan is generally that renal oncocytoma behaves benignly, as reported in other areas. The excellent prognosis associated with this tumor appears to indicate that partial nephrectomy may suffice for removing the tumor, while sparing other unaffected renal parenchyma.

Biopsy of renal masses: when and why

Percutaneous image-guided biopsy of renal masses is a safe and accurate procedure. Although once reserved for the diagnosis of unresectable renal cell carcinoma, metastases, lymphoma, and infection, today percutaneous image-guided biopsy has an expanded role. There is increasing awareness that a substantial proportion of small, solid renal masses are benign neoplasms. Although imaging can be used to diagnose most of them, some are incorrectly believed to represent renal cell carcinoma and unnecessary surgery may be performed. Based largely on advances in cytological techniques, percutaneous biopsy can be now be used to diagnose benign neoplasms and thus prevent them from being treated unnecessarily. Concurrent advances in percutaneous ablation have also promoted its use. As a result, there are 8 established indications for percutaneous biopsy, and reason to believe that the number of indications will expand further in the future.

Segmental enhancement inversion at biphasic multidetector CT: characteristic finding of small renal oncocytoma

PURPOSE

To retrospectively determine the usefulness of segmental enhancement inversion during the corticomedullary phase (CMP) and early excretory phase (EEP) of biphasic multidetector computed tomography (CT) in differentiating small renal oncocytoma from renal cell carcinoma (RCC).

MATERIALS AND METHODS

This retrospective study was institutional review board approved; informed consent was waived. Between January 2004 and December 2006, 98 patients with pathologically confirmed renal masses smaller than 4 cm (10 renal oncocytomas and 88 RCCs) were included in this study. Segmental enhancement inversion was defined as follows: In a mass with two segments showing different degrees of enhancement during CMP, the relatively highly enhanced segment became less enhanced during EEP, whereas the less-enhanced segment during CMP became highly enhanced during EEP. Two experienced radiologists retrospectively assessed the presence of segmental inversion in all masses and measured attenuation with consensus. The Fisher exact test was used to determine the significance of segmental enhancement inversion in differentiating small renal oncocytoma from RCC.

RESULTS

Eight of 10 renal oncocytomas and only one of 88 RCCs showed segmental inversion during CMP and EEP, which significantly differentiated small renal oncocytomas and RCCs (P < .0001). For differentiating oncocytoma from RCC, segmental inversion was found to have a sensitivity of 80% (eight of 10), a specificity of 99% (87 of 88), a positive predictive value of 89% (eight of nine), and a negative predictive value of 98% (87 of 89). The mean values of the attenuation differences shown by two segments during CMP and EEP were 62.75 HU +/- 36.96 (standard deviation) and -36.88 HU +/- 20.02, respectively.

CONCLUSION

Segmental enhancement inversion during CMP and EEP was found to be a characteristic enhancement pattern of small renal oncocytoma at biphasic multidetector CT and it may help in differentiating small oncocytoma from RCC.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/2522081180/DC1.

Renal cell carcinoma

Considerable progress has been made in the treatment of patients with renal cell carcinoma, with innovative surgical and systemic strategies revolutionising the management of this disease. In localised disease, partial nephrectomy for small tumours and radical nephrectomy for large tumours continue to be the gold-standard treatments, with emphasis on approaches that have reduced invasiveness and preserve renal function. Additionally, cytoreductive nephrectomy is often indicated before the start of systemic treatment in patients with metastatic disease as part of integrated management strategy. The effectiveness of immunotherapy, although previously widely used for treatment of metastatic renal cell carcinoma, is still controversial, and is mainly reserved for patients with good prognostic factors. Development of treatments that have specific targets in relevant biological pathways has been the main advance in treatment. Targeted drugs, including inhibitors of the vascular endothelial growth factor and mammalian target of rapamycin pathways, have shown robust effectiveness and offer new therapeutic options for the patients with metastatic disease.