Segmental Enhancement Inversion Research Articles

Renal Mass Imaging with MRI Clear Cell Likelihood Score: A User's Guide.

Small solid renal masses (SRMs) are frequently detected at imaging. Nearly 20% are benign, making careful evaluation with MRI an important consideration before deciding on management. Clear cell renal cell carcinoma (ccRCC) is the most common renal cell carcinoma subtype with potentially aggressive behavior. Thus, confident identification of ccRCC imaging features is a critical task for the radiologist. Imaging features distinguishing ccRCC from other benign and malignant renal masses are based on major features (T2 signal intensity, corticomedullary phase enhancement, and the presence of microscopic fat) and ancillary features (segmental enhancement inversion, arterial-to-delayed enhancement ratio, and diffusion restriction). The clear cell likelihood score (ccLS) system was recently devised to provide a standardized framework for categorizing SRMs, offering a Likert score of the likelihood of ccRCC ranging from 1 (very unlikely) to 5 (very likely). Alternative diagnoses based on imaging appearance are also suggested by the algorithm. Furthermore, the ccLS system aims to stratify which patients may or may not benefit from biopsy. The authors use case examples to guide the reader through the evaluation of major and ancillary MRI features of the ccLS algorithm for assigning a likelihood score to an SRM. The authors also discuss patient selection, imaging parameters, pitfalls, and areas for future development. The goal is for radiologists to be better equipped to guide management and improve shared decision making between the patient and treating physician. © RSNA, 2023 Quiz questions for this article are available in the supplemental material. See the invited commentary by Pedrosa in this issue.

Value of clear cell likelihood score in differentiation between renal oncocytoma and clear cell renal cell carcinoma

Objective: To evaluate the value of clear cell likelihood score (ccLS) in identifying renal oncocytoma (RO) and clear cell renal cell carcinoma (ccRCC). Methods: Retrospective data of pathologically confirmed 43 RO patients [24 men and 19 women, aged 22-77 (54±14) years] between February 2008 and September 2021 and 43 ccRCC patients [30 men and 13 women, aged 29-78 (56±12) years] between May and July 2021 were consecutively included in the department of radiology, Chinese PLA General Hospital. Two radiologists used ccLS to assess each case independently, and disagreements were resolved by consensus. The ability of ccLS to identify RO and ccRCC was examined by the receiver operating characteristic (ROC) curve which identified the best optimal diagnostic cut-off values, sensitivity, specificity, accuracy, positive predictive value, and negative predictive value. Results: The mean tumor diameter was 3.8 cm in RO patients and 3.7 cm in ccRCC patients. Central scar and segmental enhancement inversion (SEI) were more frequently observed in the RO group compared to the ccRCC group [53.5% (23∶43) versus 11.6% (5∶43) and 41.9% (18∶43) versus 7.0% (3∶43), respectively], with statistical differences (P<0.001). The ccLS scores in the RO group ranged from 1 to 4, while 79.0% of the cases were 3. The ccLS scores in the ccRCC group ranged from 2 to 5, while 72% of the cases were 4. The scores of the two groups were statistically different (P<0.001). The ccLS showed the best performance when the threshold was 4 according to the ROC curve. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of ccLS for distinguishing RO from ccRCC were 83.7%, 90.7%, 87.2%, 90.0%, and 84.8%, respectively, and the area under the ROC curve value was 0.879. Conclusion: The ccLS has credible sensitivity and specificity in differentiating renal oncocytoma from clear cell carcinoma, which may be helpful for the preoperative diagnosis.

Role of computed tomography features in the differential diagnosis of chromophobe renal cell carcinoma from oncocytoma and angiomyolipoma without visible fat.

Chromophobe renal cell carcinoma (chRCC) is often confused with oncocytoma and angiomyolipoma without visible fat (AML.wovf). The aim of this study was to determine computed tomography (CT) features predictive of chRCC to distinguish it from oncocytoma and AML.wovf. This multicenter study enrolled 38 patients with chRCC, 32 with oncocytoma, and 43 with AML.wovf of the kidney. The clinical and imaging features of all cases were reviewed retrospectively, and associations between the features and histopathology were analyzed using univariate analysis, followed by multinomial logistic regression analysis. Receiver operating characteristic (ROC) curve analysis was used to evaluate logistic regression models and determine optimal cut-off values for numeric data. Univariate analysis revealed significant differences between chRCC and oncocytoma in tumor ratios of lesion to renal cortex net enhancement (RLRCNE) on both corticomedullary and nephrographic phase images (P<0.001 for both) and calcification (P=0.035). On multinomial logistic regression analysis, only corticomedullary RLRCNE remained an independent predictor for the differential diagnosis of chRCC from oncocytoma (P<0.001), with an optimal cut-off value of 0.53. Comparing chRCC and AML.wovf, univariate analysis revealed significant differences in age (P=0.003), segmental enhancement inversion (SEI) (P=0.006), corticomedullary RLRCNE (P<0.001), unenhanced ratio of lesion to renal cortex attenuation (RLRCA; P<0.001), size (P<0.001), enhancement pattern over time (P=0.017), angle (P=0.014), and central scar (P<0.001). Only unenhanced RLRCA (P<0.001), size (P=0.003), and enhancement pattern over time (P=0.002) remained as independent predictors on multinomial logistic regression analysis, with optimal cut-off values of 1.13 and 30.9 mm for RLRCA and size, respectively. On ROC curve analysis of the logistic regression models, the areas under curve (AUC) were 0.888 and 0.963 for chRCC versus oncocytoma and AML.wovf, respectively. Corticomedullary RLRCNE on CT images was an independent predictor for the differential diagnosis of chRCC from oncocytoma. Unenhanced RLRCA, size, and enhancement pattern over time on CT had predictive value for discriminating chRCC from AML.wovf.

A CT-based radiomics nomogram for differentiation of renal oncocytoma and chromophobe renal cell carcinoma with a central scar-matched study.

Pre-operative differentiation between renal oncocytoma (RO) and chromophobe renal cell carcinoma (chRCC) is critical due to their different clinical behavior and different clinical treatment decisions. The aim of this study was to develop and validate a CT-based radiomics nomogram for the pre-operative differentiation of RO from chRCC. A total of 141 patients (84 in training data set and 57 in external validation data set) with ROs (n = 47) or chRCCs (n = 94) were included. Radiomics features were extracted from tri-phasic enhanced-CT images. A clinical model was developed based on significant patient characteristics and CT imaging features. A radiomics signature model was developed and a radiomics score (Rad-score) was calculated. A radiomics nomogram model incorporating the Rad-score and independent clinical factors was developed by multivariate logistic regression analysis. The diagnostic performance was evaluated and validated in three models using ROC curves. Twelve features from CT images were selected to develop the radiomics signature. The radiomics nomogram combining a clinical factor (segmental enhancement inversion) and radiomics signature showed an AUC value of 0.988 in the validation set. Decision curve analysis revealed that the diagnostic performance of the radiomics nomogram was better than the clinical model and the radiomics signature. The radiomics nomogram combining clinical factors and radiomics signature performed well for distinguishing RO from chRCC. Differential diagnosis between renal oncocytoma (RO) and chromophobe renal cell carcinoma (chRCC) is rather difficult by conventional imaging modalities when a central scar was present.A radiomics nomogram integrated with the radiomics signature, demographics, and CT findings facilitates differentiation of RO from chRCC with improved diagnostic efficacy.The CT-based radiomics nomogram might spare unnecessary surgery for RO.

Differential diagnosis of renal oncocytoma and chromophobe renal cell carcinoma using CT features: a central scar-matched retrospective study.

Renal oncocytoma (RO) and chromophobe renal cell carcinoma (chRCC) have a common cellular origin and different clinical management and prognosis. To explore the utility of computed tomography (CT) in the differentiation of RO and chRCC. Twenty-five patients with RO and 73 patients with chRCC presenting with the central scar were included retrospectively. Two experienced radiologists independently reviewed the CT imaging features, including location, tumor size, relative density ratio, segmental enhancement inversion (SEI), necrosis, and perirenal fascia thickening, among others. Interclass correlation coefficient (ICC, for continuous variables) or Kappa coefficient test (for categorical variables) was used to determine intra-observer and inter-observer bias between the two radiologists. The inter- and intra-reader reproducibility of the other CT imaging parameters were nearly perfect (>0.81) except for the measurements of fat (0.662). RO differed from chRCC in the cortical or medullary side (P = 0.005), relative density ratio (P = 0.020), SEI (P < 0.001), and necrosis (P = 0.045). The logistic regression model showed that location (right kidney), hypo-density on non-enhanced CT, SEI, and perirenal fascia thickening were highly predictive of RO. The combined indicators from logistic regression model were used for ROC analysis. The area under the ROC curve was 0.923 (P < 0.001). The sensitivity and specificity of the four factors combined for diagnosing RO were 88% and 86.3%, respectively. The correlation coefficient between necrosis and tumor size in all tumors including both of RO and chRCC was 0.584, indicating a positive correlation (P < 0.001). The CT imaging features of location (right kidney), hypo-density on non-enhanced CT, SEI, and perirenal fascia thickening were valuable indicators in distinguishing RO from chRCC.

Computed Tomography and Magnetic Resonance Imaging Findings and Differential Diagnosis of the Renal Oncocytoma

Objective: To discuss the imaging features of renal oncocytoma, and to improve the preoperative diagnostic accuracy. Methods: Radiology data of 16 renal oncocytoma patients were analyzed retrospectively. All the cases were confirmed by pathology. All patients underwent pre-contrast and multiple phase contrast scanning on multi-slice CT. The patients also underwent MRI examination. Results: All patients had solitary lesion, the location of oncocytoma were in right kidney (n = 9) and left kidney (n = 7). Round or round-like shape, clear boundary, protruding mass. Isodense or slightly higher density on CT pre-contrast scanning, among them, 2 cases developed into the renal sinus, 2 cases with calcification. 13 lesions showed obvious enhancement on the cortical phase, and on the medullary phase showed continuous enhancement. 4 lesions showed segmental enhancement inversion and central stellate scar was found in 8 lesions. Bleeding, necrosis, cystic change or fatty change was rare. 9 lesions showed tortuous expansion of the support vessel on the cortical phase, 6 lesions with invasion to the perirenal fat tissue. In our study, 3 samples of lesions underwent MR examination, which showed iso/hypo-intensity on T1WI. On T2WI, 1 lesion showed slightly lower signal, 2 lesion showed mixed signal. Clear pseudocapsule was revealed in MR imaging. Enhanced scan showed mild continuous enhancement. Conclusion: Most of the oncocytomas showed certain characteristic imaging, multiple phase contrast scanning are helpful in the accurate preoperative diagnosis.

MRI features of renal oncocytoma

Objective To investigate the MRI features of renal oncocytoma (RO). Methods We retrospectively analyzed the data of 26 patients by histologically confirmed with RO in Chinese PLA General Hospital from September 2006 to May 2017 and performed pre-operative MRI and dynamic contrast-enhanced MRI. Lesions were divided into two groups based on the diameter: large group with large than 3 cm (16 cases, 16 lesions) and small group with less than 3 cm (10 cases, 11 lesions). Features of each lesion were analyzed, including location, pseudocapsules, lipids and other 11 indicators. Tumor imaging features were compared between two groups by univariate and multivariate logistic regression analysis. Results Of 27 RO lesions, 12 were located in the left kidney and 15 in the right kidney. Twenty five lesions appeared exophytic (92.6%, 25/27), 10 lesions showed exophytic angular interface (37.0%, 10/27), 25 lesions showed pseudocapsule (92.6%, 25/27), 4 lesions appeared lipid (14.8%, 4/27), 2 lesions showed cystic degeneration or necrosis (7.4%, 2/27), 1 lesion showed hemorrhage (3.7%, 1/27), 13 lesions appeared fibrous scar (48.1%, 13/27), 19 lesions with moderate or intense enhancement in the corticomedullary phase (70.4%, 19/27), 9 lesions with wheel-spoke-like enhancement (33.3%, 9/27), and 2 lesions showed segmental enhancement inversion (7.4%, 2/27). Univariate logistic regression exhibited statistically significant correlation between exophytic angular interface with renal parenchyma, fibrous scar, moderate or intense enhancement in the corticomedullary phase, and wheel-spoke-like enhancement of the tumors both in small and large RO groups with OR value of 0.054, 9.898, 8.400 and 10.000, respectively. In the multivariate logistic regression analysis, exophytic angular interface with renal parenchyma and intense enhancement in the corticomedullary phase were found to be high risk factors with OR value of 0.033 and 15.381, respectively. Conclusions The main manifestation of RO on MRI is that both kidneys can occur, with many exogenesis, pseudocapsules, but less lipids, cystic degeneration, necrosis, hemorrhage and segmental enhanced reversal;smaller lesions (diameter<3 cm) tend to conical interface, while larger lesions (diameter ≥ 3 cm) may have fibrous scars, spoke-shaped enhancement, moderate and significantly enhanced cortical phase characteristics. Key words: Kidney neoplasms; Renal oncocytoma; Magnetic resonance imaging

Characterization of small (

Diagnosis of renal cell carcinomas (RCC) subtypes on computed tomography (CT) and magnetic resonance imaging (MRI) is clinically important. There is increased evidence that confident imaging diagnosis is now possible while standardization of the protocols is still required. Fat-poor angiomyolipoma show homogeneously increased unenhanced attenuation, homogeneously low signal on T2-weighted MRI and apparent diffusion coefficient (ADC) map, may contain microscopic fat and are classically avidly enhancing. Papillary RCC are also typically hyperattenuating and of low signal on T2-weighted MRI and ADC map; however, their gradual progressive enhancement after intravenous administration of contrast material is a differentiating feature. Clear cell RCC are avidly enhancing and may show intracellular lipid; however, these tumors are heterogeneous and are of characteristically increased signal on T2-weighted MRI. Oncocytomas and chromophobe tumors (collectively oncocytic neoplasms) show intermediate imaging findings on CT and MRI and are the most difficult subtype to characterize accurately; however, both show intermediately increased signal on T2-weighted with more gradual enhancement compared to clear cell RCC. Chromophobe tumors tend to be more homogeneous compared to oncocytomas, which can be heterogeneous, but other described features (e.g. scar, segmental enhancement inversion) overlap considerably between tumors. Tumor grade is another important consideration in small solid renal masses with emerging studies on both CT and MRI suggesting that high grade tumors may be separated from lower grade disease based upon imaging features.

Diagnostic Performance and Interreader Agreement of a Standardized MR Imaging Approach in the Prediction of Small Renal Mass Histology.

Purpose To assess the diagnostic performance and interreader agreement of a standardized diagnostic algorithm in determining the histologic type of small (≤4 cm) renal masses (SRMs) with multiparametric magnetic resonance (MR) imaging. Materials and Methods This single-center retrospective HIPAA-compliant institutional review board-approved study included 103 patients with 109 SRMs resected between December 2011 and July 2015. The requirement for informed consent was waived. Presurgical renal MR images were reviewed by seven radiologists with diverse experience. Eleven MR imaging features were assessed, and a standardized diagnostic algorithm was used to determine the most likely histologic diagnosis, which was compared with histopathology results after surgery. Interreader variability was tested with the Cohen κ statistic. Regression models using MR imaging features were used to predict the histopathologic diagnosis with 5% significance level. Results Clear cell renal cell carcinoma (RCC) and papillary RCC were diagnosed, with sensitivities of 85% (47 of 55) and 80% (20 of 25), respectively, and specificities of 76% (41 of 54) and 94% (79 of 84), respectively. Interreader agreement was moderate to substantial (clear cell RCC, κ = 0.58; papillary RCC, κ = 0.73). Signal intensity (SI) of the lesion on T2-weighted MR images and degree of contrast enhancement (CE) during the corticomedullary phase were independent predictors of clear cell RCC (SI odds ratio [OR]: 3.19; 95% confidence interval [CI]: 1.4, 7.1; P = .003; CE OR, 4.45; 95% CI: 1.8, 10.8; P < .001) and papillary RCC (CE OR, 0.053; 95% CI: 0.02, 0.2; P < .001), and both had substantial interreader agreement (SI, κ = 0.69; CE, κ = 0.71). Poorer performance was observed for chromophobe histology, oncocytomas, and minimal fat angiomyolipomas, (sensitivity range, 14%-67%; specificity range, 97%-99%), with fair to moderate interreader agreement (κ range = 0.23-0.43). Segmental enhancement inversion was an independent predictor of oncocytomas (OR, 16.21; 95% CI: 1.0, 275.4; P = .049), with moderate interreader agreement (κ = 0.49). Conclusion The proposed standardized MR imaging-based diagnostic algorithm had diagnostic accuracy of 81% (88 of 109) and 91% (99 of 109) in the diagnosis of clear cell RCC and papillary RCC, respectively, while achieving moderate to substantial interreader agreement among seven radiologists. © RSNA, 2018 Online supplemental material is available for this article.

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).

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

Diagnostic accuracy of segmental enhancement inversion for diagnosis of renal oncocytoma at biphasic contrast enhanced CT: systematic review

To use systematic review to evaluate the diagnostic accuracy of segmental enhancement inversion (SEI) at contrast-enhanced biphasic multi-detector computed tomography (MDCT) for the diagnosis of renal oncocytoma. Several electronic databases were searched through October 2013. Two reviewers independently selected studies that met the inclusion criteria and extracted data. Study quality was assessed with the QUADAS-2 tool. The primary 2 × 2 data were investigated with forest plot and ROC plot of sensitivity and specificity. Four studies met the inclusion criteria (307 patients). Considerable heterogeneity between studies precluded meta-analysis. Two studies from the same group of investigators demonstrated reasonable diagnostic accuracy (sensitivity 59-80 % and specificity 87-99 %), while two others did not (sensitivity 0-6 %, specificity 93-100 %). Possible reasons for this include timing of biphasic MDCT and methods of interpretation but not size of lesion. SEI is a specific imaging finding of renal oncocytoma with highly variable sensitivity. This substantial heterogeneity across studies and between institutions suggests that further validation of this imaging finding is necessary prior to application in clinical practice. SEI on CT in small renal masses is specific for oncocytoma. Sensitivity of SEI varies substantially between studies and across institutions. Variability could relate to CT timing or methods of interpretation. High accuracy of SEI has only been reported by one group. Validation of SEI is needed prior to clinical implementation.

Comparison of Segmental Enhancement Inversion on Biphasic MDCT Between Small Renal Oncocytomas and Chromophobe Renal Cell Carcinomas

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

Segmental Enhancement Inversion of Small Renal Oncocytoma: Differences in Prevalence According to Tumor Size

The purpose of this study was to retrospectively assess the prevalence of segmental enhancement inversion of small renal oncocytomas according to tumor size. Thirty-three patients (19 men, 14 women; mean age, 61 years; range, 40-74 years) with 33 oncocytomas diagnosed at surgical resection who had undergone contrast-enhanced biphasic CT between January 2000 and December 2011 were included. CT scans were analyzed by two radiologists blinded to the specifics of the pathology report for size, presence of segmental enhancement inversion, enhancement pattern, and homogeneity. Segmental enhancement inversion was present when a renal mass was divided into two differently enhanced segments in the corticomedullary phase (30-40 seconds after contrast injection) with the degree of enhancement reversed in the nephrographic phase (120-180 seconds after contrast injection). The masses were further assessed for fibrous septa, cystic change, hemorrhage, and necrosis. For statistical analysis, the Pearson chi-square test and linear regression were used to evaluate the relation between the prevalence of segmental enhancement inversion and tumor size or pathologic changes. The mean diameter of 33 renal oncocytomas was 2.65 cm (range, 0.8-4.8 cm). There was no significant linear trend according to size (p = 0.762), although segmental enhancement inversion was significantly (p = 0.006) more common (10/12) in tumors measuring 1.5-2.9 cm. Pathologic change was present in 14 oncocytomas. There was no significant linear trend according to size (p = 0.068), but 2.5-cm and larger tumors had a significantly higher prevalence (57.9%) (p = 0.036). Segmental enhancement inversion was more common (13/19) in tumors without pathologic change (p = 0.024). Segmental enhancement inversion was a characteristic finding in our series of small renal oncocytomas and was more common in tumors measuring 1.5-2.9 cm. Pathologic changes such as central scar were more common in oncocytomas larger than 2.5 cm and may be related to the low occurrence of segmental enhancement inversion.

Small Renal Oncocytomas: Is Segmental Enhancement Inversion a Characteristic Finding at Biphasic MDCT?

The purpose of this study was to retrospectively determine whether segmental enhancement inversion was a common and characteristic finding in small (≤ 4 cm) renal oncocytomas on biphasic contrast-enhanced CT. This retrospective case-control study included 16 patients with 16 renal oncocytomas and 15 control patients with 15 renal cell carcinomas (RCCs), matched for age and sex, who underwent biphasic contrast-enhanced MDCT at our institution. Three reviewers independently analyzed each tumor for enhancement patterns on MDCT, including the presence or absence of segmental enhancement inversion, homogeneity, and phase of peak enhancement. The mean and median sizes of the oncocytomas were 2.5 and 2.4 cm, respectively (range, 1.1-3.9 cm), and the mean and median sizes of the RCCs were both 2.6 cm (range, 1.4-3.9 cm). There was no significant difference in the size of the renal masses between the two groups (p = 0.50). For two reviewers, segmental enhancement inversion was not present in any of the renal masses; for one reviewer, segmental enhancement inversion was present in one oncocytoma (6%) and one RCC (7%). For all reviewers, there was no feature or enhancement pattern that was statistically significantly associated with renal oncocytoma or RCC (p < 0.05). Segmental enhancement inversion was not a common or characteristic CT finding for renal oncocytoma and was not helpful in differentiating small renal oncocytomas from RCC.

Is Segmental Enhancement Inversion on Enhanced Biphasic MDCT a Reliable Sign for the Noninvasive Diagnosis of Renal Oncocytomas?

The objective of our study was to retrospectively determine whether segmental enhancement inversion or other CT patterns seen at enhanced biphasic MDCT are predictive for the diagnosis of renal oncocytoma. Twenty-nine patients with 32 oncocytomas diagnosed by either biopsy or resection who had undergone enhanced biphasic CT between January 2004 and March 2010 were included in this study. Biphasic CT scans were analyzed for the presence of segmental enhancement inversion. Segmental enhancement inversion was defined as a renal mass with two distinctive segments in which the attenuation of the segments changed between the two phases of CT. The masses were further characterized on imaging to determine if any imaging feature is predictive of renal oncocytoma. Of the 32 renal oncocytomas, 16 oncocytomas were eliminated from analysis. These masses were eliminated because they were larger than 4 cm (n = 4), the CT examinations were inadequate (n = 10), or the pathology results were questionable (n = 2). The remaining 16 tumors (mean size, 2.6 cm; range, 1.8-3.9 cm) were included in our study. Only two tumors showed distinct segments of variable degrees of enhancement, with one of those tumors having segmental enhancement inversion. Three masses had a central region of low density. The most common feature, identified in eight of the 16 oncocytomas, was a slightly heterogeneous mass that became homogeneous on the later phase of CT. Three oncocytomas had a homogeneous appearance on both phases. Contrary to a prior report, we did not find segmental enhancement inversion to be a characteristic enhancement pattern of small renal oncocytomas on biphasic MDCT. We found no specific features on biphasic CT that could be considered reliable and could strongly suggest the diagnosis of renal oncocytoma.

MRI Features of Renal Oncocytoma and Chromophobe Renal Cell Carcinoma

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). 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. 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). 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.

Segmental Enhancement Inversion at Biphasic Multidetector CT: Characteristic Finding of Small Renal Oncocytoma

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