Differentiation of pathologic subtypes of papillary renal cell carcinoma on CT

CT of the urinary tract revisited

Computed tomography (CT) of the abdomen is usually appropriate for the initial imaging of many urinary tract diseases, due to its wide availability, fast scanning and acquisition of thin slices and isotropic data, that allow the creation of multiplanar reformatted and three-dimensional reconstructed images of excellent anatomic details. Non-enhanced CT remains the standard imaging modality for assessing renal colic. The technique allows the detection of nearly all types of urinary calculi and the estimation of stone burden. CT is the primary diagnostic tool for the characterization of an indeterminate renal mass, including both cystic and solid tumors. It is also the modality of choice for staging a primary renal tumor. Urolithiasis and urinary tract malignancies represent the main urogenic causes of hematuria. CT urography (CTU) improves the visualization of both the upper and lower urinary tract and is recommended for the investigation of gross hematuria and microscopic hematuria, in patients with predisposing factors for urologic malignancies. CTU is highly accurate in the detection and staging of upper tract urothelial malignancies. CT represents the most commonly used technique for the detection and staging of bladder carcinoma and the diagnostic efficacy of CT staging improves with more advanced disease. Nevertheless, it has limited accuracy in differentiating non-muscle invasive bladder carcinoma from muscle-invasive bladder carcinoma. In this review, clinical indications and the optimal imaging technique for CT of the urinary tract is reviewed. The CT features of common urologic diseases, including ureterolithiasis, renal tumors and urothelial carcinomas are discussed.

Prognostic value of tumour contour irregularity on surgical strategies for T1bN0M0 renal cell carcinoma: A multi-institutional study

PURPOSE

To determine the prognostic value of tumour contour irregularity degree (CID) in surgical strategy options for T1bN0M0 renal cell carcinoma (RCC).

MATERIALS AND METHODS

We performed a retrospective multi-institutional review of 489 patients with T1bN0M0 RCC treated between January 2009 and June 2019. Cox regression and Kaplan-Meier analyses were performed to analyse the impact of CID on disease-free survival (DFS).

RESULTS

The median follow-up time was 55 months (interquartile range, 40-81 months) for 55 (11.2 %) patients with metastasis or recurrence. Logistic analysis indicated that CID was associated with World Health Organization/International Society of Urological Pathology (WHO/ISUP) grades III-IV (odds ratio, 1.015; 95 % confidence interval [CI], 1.008-1.023; p < 0.001). After being classified into high CID (≥50 %) and low CID (<50 %) groups, those with a high CID showed a significantly higher ratio of WHO/IUSP grades III-IV (74/277 [26.7 %] vs 25/212 [11.8 %]) and shorter DFS than the low CID group (p < 0.001). Multivariable Cox regression showed that partial nephrectomy (PN; hazard ratio [HR], 1.889; 95 % CI, 1.020-3.499; p = 0.043), high CID (HR, 6.685; 95 % CI, 2.776-16.100; p < 0.001), and WHO/ISUP grade III-IV (HR, 1.950; 95 % CI, 1.100-3.458; p = 0.022) were independent prognostic factors for DFS. The Kaplan-Meier plot showed that PN had a DFS rate comparable to that of radical nephrectomy (RN; p = 0.994). In the low CID group, patients who underwent PN showed comparable DFS to those who underwent RN (p = 0.903). Furthermore, patients with a high CID tended to have worse DFS in the PN versus RN group (p = 0.044). Multivariable Cox regression showed that PN (HR, 2.049; 95 % CI, 1.065-3.942; p = 0.032) and WHO/ISUP grade III-IV (HR, 2.148; 95 % CI, 1.189-3.881; p = 0.011) were independent prognostic factors of DFS in the high CID group.

CONCLUSIONS

CID is a reliable preoperative parameter which is positively correlated with WHO/ISUP grade and can help with surgical decision-making in patients with T1bN0M0 RCC.

The value of CT features and demographic data in the differential diagnosis of type 2 papillary renal cell carcinoma from fat-poor angiomyolipoma and oncocytoma

PURPOSES

To determine the CT features and demographic data predictive of type 2 papillary renal cell carcinoma (PRCC) that can help distinguish this neoplasm from fat-poor angiomyolipoma (fpAML) and oncocytoma.

METHODS

Fifty-four patients with type 2 PRCC, 48 with fpAML, and 47 with oncocytoma in the kidney from multiple centers were retrospectively reviewed. The demographic data and CT features of type 2 PRCC were analyzed and compared with those of fpAML and oncocytoma by univariate analysis and multiple logistic regression analysis to determine the predictive factors for differential diagnosis. Then, receiver operating characteristic (ROC) curve analysis was performed to further assess the logistic regression model and set the threshold level values of the numerical parameters.

RESULTS

Older age (≥ 46.5 years), unenhanced lesion-to-renal cortex attenuation (RLRCA) < 1.21, corticomedullary ratio of lesion to renal cortex net enhancement (RLRCNE) < 0.32, and size ≥ 30.1 mm were independent predictors for distinguishing type 2 PRCC from fpAML (OR 14.155, 8.332, and 57.745, respectively, P < 0.05 for all). The area under the curve (AUC) of the multiple logistic regression model in the ROC curve analysis was 0.970. In the combined evaluation, the four independent predictors had a sensitivity and specificity of 0.896 and 0.889, respectively. A corticomedullary RLRCNE < 0.61, irregular shape, and male sex were independent predictors for the differential diagnosis of type 2 PRCC from oncocytoma (OR 15.714, 12.158, and 6.175, respectively, P < 0.05 for all). In the combined evaluation, the three independent predictors had a sensitivity and specificity of 0.889 and 0.979, respectively. The AUC of the multiple logistic regression model in the ROC curve analysis was 0.964.

CONCLUSION

The combined application of CT features and demographic data had good ability in distinguishing type 2 PRCC from fpAML and oncocytoma, respectively.

MR Spectroscopy for Detecting Fumarate Hydratase Deficiency in Hereditary Leiomyomatosis and Renal Cell Carcinoma Syndrome

Background Noninvasive in vivo detection of fumarate accumulation may help identify fumarate hydratase deficiency in renal cancer related to hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome. Purpose To investigate the feasibility of MR spectroscopy (MRS) in detecting elevated fumarate levels in HLRCC-associated renal cancers. Materials and Methods This study included an experimental xenograft mouse model and prospective clinical cohort. First, MRS was performed on patient-derived tumor xenograft models and control models to detect fumarate. Then, consecutive participants with clinical suspicion of HLRCC-associated renal tumors were enrolled. For the detection of fumarate, MRS results were classified as detected, borderline, undetected, or technical failure. The sensitivity, specificity, and accuracy of MRS for diagnosing HLRCC-associated renal cancer were assessed. The signal-to-noise ratio (SNR) of the fumarate peak was calculated and evaluated with receiver operating characteristic curve analysis. Results Fumarate peaks were detected at 6.54 parts per million in all three patient-derived xenograft models. A total of 38 participants (21 men; mean age, 47 years [range, 18-71 years]) with 46 lesions were analyzed. All primary HLRCC-associated renal cancers showed a fumarate peak; among the seven metastatic HLRCC-associated lesions, a fumarate peak was detected in three lesions and borderline in two. When only detected peaks were regarded as positive findings, the sensitivity, specificity, and accuracy of MRS at the lesion level were 69% (nine of 13 lesions), 100% (33 of 33 lesions), and 91% (42 of 46 lesions), respectively. When borderline peaks were also included as a positive finding, the sensitivity, specificity, and accuracy reached 85% (11 of 13 lesions), 88% (29 of 33 lesions), and 87% (40 of 46 lesions), respectively. The SNR of fumarate showed an area under the receiver operating characteristic curve of 0.87 for classifying HLRCC-associated tumors. Conclusion MR spectroscopy of fumarate was sensitive and specific for hereditary leiomyomatosis and renal cell carcinoma-associated tumors. © RSNA, 2022 Online supplemental material is available for this article.

Differential Diagnosis of Type 1 and Type 2 Papillary Renal Cell Carcinoma Based on Enhanced CT Radiomics Nomogram

Objectives

To construct a contrast-enhanced CT-based radiomics nomogram that combines clinical factors and a radiomics signature to distinguish papillary renal cell carcinoma (pRCC) type 1 from pRCC type 2 tumours.

Methods

A total of 131 patients with 60 in pRCC type 1 and 71 in pRCC type 2 were enrolled and divided into training set (n=91) and testing set (n=40). Patient demographics and enhanced CT imaging characteristics were evaluated to set up a clinical factors model. A radiomics signature was constructed and radiomics score (Rad-score) was calculated by extracting radiomics features from contrast-enhanced CT images in corticomedullary phase (CMP) and nephrographic phase (NP). A radiomics nomogram was then built by incorporating the Rad-score and significant clinical factors according to multivariate logistic regression analysis. The diagnostic performance of the clinical factors model, radiomics signature and radiomics nomogram was evaluated on both the training and testing sets.

Results

Three validated features were extracted from the CT images and used to construct the radiomics signature. Boundary blurring as an independent risk factor for tumours was used to build clinical factors model. The AUC value of the radiomics nomogram, which was based on the selected clinical factors and Rad-score, were 0.855 and 0.831 in the training and testing sets, respectively. The decision curves of the radiomics nomogram and radiomics signature in the training set indicated an overall net benefit over the clinical factors model.

Conclusion

Radiomics nomogram combining clinical factors and radiomics signature is a non-invasive prediction method with a good prediction for pRCC type 1 tumours and type 2 tumours preoperatively and has some significance in guiding clinicians selecting subsequent treatment plans.

Long Non-Coding RNAs as Novel Biomarkers in the Clinical Management of Papillary Renal Cell Carcinoma Patients: A Promise or a Pledge?

Papillary renal cell carcinoma (pRCC) represents the second most common subtype of renal cell carcinoma, following clear cell carcinoma and accounting for 10–15% of cases. For around 20 years, pRCCs have been classified according to their mere histopathologic appearance, unsupported by genetic and molecular evidence, with an unmet need for clinically relevant classification. Moreover, patients with non-clear cell renal cell carcinomas have been seldom included in large clinical trials; therefore, the therapeutic landscape is less defined than in the clear cell subtype. However, in the last decades, the evolving comprehension of pRCC molecular features has led to a growing use of target therapy and to better oncological outcomes. Nonetheless, a reliable molecular biomarker able to detect the aggressiveness of pRCC is not yet available in clinical practice. As a result, the pRCC correct prognosis remains cumbersome, and new biomarkers able to stratify patients upon risk of recurrence are strongly needed. Non-coding RNAs (ncRNAs) are functional elements which play critical roles in gene expression, at the epigenetic, transcriptional, and post-transcriptional levels. In the last decade, ncRNAs have gained importance as possible biomarkers for several types of diseases, especially in the cancer universe. In this review, we analyzed the role of long non-coding RNAs (lncRNAs) in the prognosis of pRCC, with a particular focus on their networking. In fact, in the competing endogenous RNA hypothesis, lncRNAs can bind miRNAs, resulting in the modulation of the mRNA levels targeted by the sponged miRNA, leading to additional regulation of the target gene expression and increasing complexity in the biological processes.

Predictive value of renal tumor contour irregularity score in pathological T3a upstaging of clinical T1 renal cell carcinoma: A multi-institutional study

PURPOSE

To explore the predictive value of renal tumor contour irregular degree (CID) in pathological T3a upstaging of clinical T1 renal cell carcinoma (RCC).

MATERIALS AND METHODS

We performed a retrospective multi-institutional review of 1,487 patients with clinical T1N0M0 RCC between January 2009 and June 2019. Kaplan-Meier survival curve and Cox regressions were used to analyze the prognostic factors of disease-free survival (DFS). Logistic regressions were performed to determine predictors of pathological T3a upstaging in clinical T1 RCC.

RESULTS

Among 1,487 patients with cT1 RCC, 96 (6.5%) were pathological T3a upstaging. Multivariable logistic regression analysis showed that age (odds ratio [OR] = 1.022, 95% confidence interval [CI] = 1.001-1.042, P = 0.036), tumor maximum diameter(OR = 1.242, 95% CI = 1.042--1.480, P = 0.015) and CID (OR = 1.067, 95% CI = 1.051-1.083, P < 0.001) were independent predictors of pathological T3a upstaging. The area under the curve (AUC) of the prediction model that included the CID was 0.846, while the AUC of the prediction model that did not include CID was only 0.741, the difference was statistically significant (P < 0.001). Kaplan-Meier survival curve showed that patients with pathological T3a upstaging had significantly worse DFS than patients without pathological T3a upstaging (P < 0.001). Multivariable Cox analysis showed that pathological T3a upstaging (HR = 1.836, 95% CI = 1.013-3.329, P = 0.002) is an independent prognostic factor for DFS in patients with cT1N0M0 RCC.

CONCLUSIONS

The predictive model of CID combined with tumor maximum diameter and age significantly improved the ability to predict pathological T3a upstaging in clinical T1 RCC, compared with the prediction model of tumor maximum diameter combined with age. The predictive model of CID combined with tumor maximum diameter and age may be applicable to patients considering partial vs. radical nephrectomy.

Value of energy spectrum CT parameters in the differential diagnosis of high-grade clear cell renal cell carcinoma and type II papillary renal cell carcinoma

BACKGROUND

Energy spectrum computed tomography (CT) has become a promising approach for the differential diagnosis of tumor subtypes.

PURPOSE

To explore the value of energy spectrum CT parameters in the differential diagnosis of high-grade clear cell renal cell carcinoma (ccRCC) and type II papillary renal cell carcinoma (pRCC).

MATERIAL AND METHODS

Forty-two cases of high-grade ccRCC and 28 cases of type II pRCC were retrospectively reviewed. All region of interest (ROI) measurements were maintained consistently between the two-phase contrast-enhanced examinations. The ROIs encompassed as much of the enhancing areas of the lesions as possible. Energy spectrum CT parameters of all cases, including the 70 keV (HU) value, normalized iodine concentration (NIC), and energy spectrum curve slope were recorded by two radiologists with over 10 years of experience in abdominal CT diagnosis.

RESULTS

In the cortical phase (CP) and parenchymal phase (PP), the 70 keV (HU) value, NIC, and slope value of the energy spectrum curve of high-grade ccRCC were significantly higher than those of type II pRCC. In the CP, NIC showed the highest differential diagnosis efficiency for the two group tumors, with a sensitivity of 78.9% and a specificity of 77.0%. There was no statistical difference in tumor hemorrhage, tumor envelope, tumor morphology, tumor border, lymph node metastasis, embolism, renal pelvis invasion, or tumor calcification between the two tumor types. However, there was significant difference in the number of tumors (P = 0.019).

CONCLUSION

Energy spectrum CT parameters are valuable for the differential diagnosis of high-grade ccRCC and type II pRCC.

Functional magnetic resonance imaging for distinguishing type of papillary renal cell carcinoma: a preliminary study

OBJECTIVE

To investigate the feasibility of magnetic resonance diffusion kurtosis imaging (DKI) and intravoxel incoherent motion (IVIM) for distinguishing Type 1 and 2 of papillary renal cell carcinoma (PRCC).

METHODS

A total of Type 1 (n = 20) and Type 2 (n = 16) of PRCC were examined by pathology. For DKI and IVIM, mean diffusivity (MD), fractional anisotropy (FA), mean kurtosis (MK), kurtosis anisotropy (KA), radial kurtosis (RK), diffusivity (D), pseudodiffusivity (D*) and perfusion fraction (f) were performed in assessment of type of PRCC.

RESULTS

The mean SNRs of IVIM and DKI images at b = 1500 and 2000 s/mm² were 8.6 ± 0.8 and 7.8 ± 0.6. Statistically significant differences were observed in MD and D values (1.11 ± 0.23 vs 0.73 ± 0.13, 0.91 ± 0.24 vs 0.49 ± 0.13, p < 0.05) between Type 1 and Type 2 of PRCC, while comparable FA, RK, D* and f values were found between Type 1 and Type 2 of PRCC (p > 0.05). Statistically significant differences were observed in MK and KA values (1.23 ± 0.16 vs 1.91 ± 0.26, 1.49 ± 0.19 vs 2.36 ± 0.39, p < 0.05) between Type 1 and Type 2 of PRCC. Areas of MD, MK, KA and D values under ROC curves for differentiating Type 1 and Type 2 of PRCC were 0.836, 0.818, 0.881 and 0.766, respectively. Using MD, MK, KA and D values of 0.93, 1.64, 1.94, 0.68 as the threshold value for differentiating Type 1 from Type 2 of PRCC, the best result obtained had a sensitivity of 85.0%, 80.0%, 90.0%, 85.0%, a specificity 75.0%, 68.7%, 87.5%, 81.2%, and an accuracy of 83.3%, 80.5%, 88.9%, 86.1%, respectively.

CONCLUSION

DKI and IVIM are feasible techniques for distinguishing type of PRCC, given an adequate SNR of IVIM and DKI images.

ADVANCES IN KNOWLEDGE

1. MD and D values are higher for Type 1 of PRCC and lower for Type 2 of PRCC.2. MK and KA values are higher for Type 2 of PRCC and lower for Type 1 of PRCC.3. DKI and IVIM can be used as clinical biomarker for PRCC type's differential diagnosis, given an adequate SNR.

Prediction of histologic grade and type of small (< 4 cm) papillary renal cell carcinomas using texture and neural network analysis: a feasibility study

OBJECTIVE

To predict the histologic grade and type of small papillary renal cell carcinomas (pRCCs) using texture analysis and machine learning algorithms.

METHODS

This was a retrospective HIPAA-compliant study. 24 noncontrast (NC), 22 corticomedullary (CM) phase, and 24 nephrographic (NG) phase CTs of small (< 4 cm) surgically resected pRCCs were identified. Surgical pathology classified the tumors as low- or high-Fuhrman histologic grade and type 1 or 2. The axial image with the largest cross-sectional tumor area was exported and segmented. Six histogram and 31 texture (20 gray-level co-occurrences and 11 gray-level run-lengths) features were calculated for each tumor in each phase. Feature values in low- versus high-grade and type 1 versus 2 pRCCs were compared. Area under the receiver operating curve (AUC) was calculated for each feature to assess prediction of histologic grade and type of pRCCs in each phase. Histogram, texture, and combined histogram and texture feature sets were used to train and test three classification algorithms (support vector machine (SVM), random forest, and histogram-based gradient boosting decision tree (HGBDT)) with stratified shuffle splits and threefold cross-validation; AUCs were calculated for each algorithm in each phase to assess prediction of histologic grade and type of pRCCs.

RESULTS

Individual histogram and texture features did not have statistically significant differences between low- and high-grade or type 1 and type 2 pRCCs across all phases. Individual features had low predictive power for tumor grade or type in all phases (AUC < 0.70). HGBDT was highly accurate at predicting pRCC histologic grade and type using histogram, texture or combined histogram and texture feature data from the CM phase (AUCs = 0.97-1.0). All algorithms had highest AUCs using CM phase feature data sets; AUCs decreased using feature sets from NC or NG phases.

CONCLUSIONS

The histologic grade and type of small pRCCs can be predicted with classification algorithms using CM histogram and texture features, which outperform NC and NG phase image data. The accurate prediction of pRCC histologic grade and type may be able to further guide management of patients with small (< 4 cm) pRCCs being considered for active surveillance.

The effect of the papillary renal cell carcinoma subtype on oncological outcomes

The study aimed to compare the clinicopathological features and prognosis between type I and type II papillary renal cell carcinoma (PRCC) and to investigate whether the subtypes of PRCC would affect oncological outcomes. A total of 102 patients with PRCC were recruited, of which 42 were type I PRCC and 60 type II. The clinicopathological features and oncologic outcomes of the patients were evaluated. The type II cases had a higher WHO/ISUP grading (P < 0.001), T (P = 0.003), N (P = 0.010) stage and stage grouping (P = 0.011) than the type I. During a median follow-up period of 61.4 months, 1-year cancer specific survival (CSS) of the type I was 100%, 5-year CSS was 95.2%, the 1-year CSS of the type II was 96.2%, and 5-year CSS was 75.7%. The univariate analysis showed that subtype, symptoms, TNM, stage grouping, WHO/ISUP grading and surgical methods appeared to affect prognosis of the patients with PRCC. However, multivariate analysis revealed that only stage grouping was the independent risk factor. After the stage grouping factor was adjusted for the analysis, there were no statistically significant differences in CSS (P = 0.214) and PFS (P = 0.190) between the localized type I and type II PRCC groups. Compared with type I PRCC, type II had higher pathological T, N stage and WHO/ISUP grading. However, it was the Stage grouping that made a great difference to oncological outcomes, rather than the subtype of PRCC.

Tumor contour irregularity on preoperative imaging: a practical and useful prognostic parameter for papillary renal cell carcinoma

OBJECTIVES

To illustrate tumor contour irregularity on preoperative imaging with a practical method and further determine its value in predicting disease-free survival (DFS) in patients with pRCC (papillary renal cell carcinoma).

METHODS

We performed a retrospective single-institution review of 267 Chinese pRCC patients between March 2009 and May 2019. Contour irregularity on cross-section was classified into smooth but distorted margin, unsmooth and sharply nodular margin, and blurred margin. Then, the ratio of the cross-section numbers of irregularity and the total tumor was defined as the contour irregular degree (CID). Cox regression and Kaplan-Meier analysis were performed to analyze the impact of CID on DFS. Then, the prognostic performance of CID was compared with pRCC risk stratification published by Leibovich et al. RESULTS: The median follow-up was 45 months (IQR: 23-69), in which 27 (10%) patients had metastasis or recurrence. Observed DFS rates were 95%, 90%, and 88% at 1, 3, and 5 years. The CID was an independent prognostic factor of DFS (HR = 1.048, 95% CI = 1.029-1.068, p < 0.001). The Kaplan-Meier plot showed that high-risk patients (CID ≥ 50%) tended to have a significantly shorter DFS (p < 0.001). The CID and Leibovich's pRCC model for DFS prediction had a C-index of 0.934 (95% CI = 0.907-0.961) and 0.833 (95% CI = 0.739-0.927) respectively.

CONCLUSIONS

With our standard and practical method, the CID can be a reliable imaging marker for DFS prediction in patients with pRCC.

KEY POINTS

• The updated contour irregularity was an independent parameter for predicting disease-free survival in patients with pRCC. • High-risk pRCC patients (contour irregular degree ≥ 50%) tended to have a shorter disease-free survival. • Tumor contour irregularity in pRCC risk stratification outperformed Leibovich's model from our cohort.

CT texture analysis for the differentiation of papillary renal cell carcinoma subtypes

PURPOSE

The objective of this study was to investigate whether computed tomography texture analysis can be used to differentiate papillary renal cell carcinoma (PRCC) subtypes.

METHOD

Sixty-two PRCC tumors were retrospectively evaluated, with 30 type 1 tumors and 32 type 2 tumors. Texture parameters quantified from three-phase contrast-enhanced CT images were compared with least absolute shrinkage and selection operator (LASSO) regression. Receiver operating characteristic (ROC) analysis was performed, and the area under the ROC curve (AUC) was calculated for each parameter. The selected texture parameters of each phase were used to generate support vector machine (SVM) classifiers. Decision curve analysis (DCA) of the classification was performed.

RESULTS

The two texture parameters with the top two AUC values were - 333-7 Correlation (AUC = 0.772) and 45-7 Entropy (AUC = 0.753) in the corticomedullary phase, 333-4 Correlation (AUC = 0.832) and 45-7 Entropy (AUC = 0.841) in the nephrographic phase, and 135-7 Entropy (AUC = 0.858) and - 333-1 InformationMeasureCorr2 (AUC = 0.849) in the excretory phase. Entropy and Correlation have a high correlation with the two types of PRCC and are increased in type 2 PRCC. A model incorporating the texture parameters with the top two AUC values in each phase produced an AUC of 0.922 with an accuracy of 84% (sensitivity = 89% and specificity = 80%). The nephrographic-phase model and the model combining the texture parameters of the three phases can differentiate the two types with the largest net benefit.

CONCLUSIONS

Computed tomography texture analysis can be used to distinguish type 2 PRCC from type 1 with high accuracy, which may be clinically important.

Clinical Importance of Incidental Homogeneous Renal Masses That Measure 10-40 mm and 21-39 HU at Portal Venous Phase CT: A 12-Institution Retrospective Cohort Study

BACKGROUND. Incidental homogeneous renal masses are frequently encountered at portal venous phase CT. The American College of Radiology Incidental Findings Committee's white paper on renal masses recommends additional imaging for incidental homogeneous renal masses greater than 20 HU, but single-center data and the Bosniak classification version 2019 suggest the optimal attenuation threshold for detecting solid masses should be higher. OBJECTIVE. The purpose of this article is to determine the clinical importance of small (10-40 mm) incidentally detected homogeneous renal masses measuring 21-39 HU at portal venous phase CT. METHODS. We performed a 12-institution retrospective cohort study of adult patients who underwent portal venous phase CT for a nonrenal indication. The date of the first CT at each institution ranged from January 1, 2008, to January 1, 2014. Consecutive reports from 12,167 portal venous phase CT examinations were evaluated. Images were reviewed for 4529 CT examinations whose report described a focal renal mass. Eligible masses were 10-40 mm, well-defined, subjectively homogeneous, and 21-39 HU. Of these, masses that were shown to be solid without macroscopic fat; classified as Bosniak IIF, III, or IV; or confirmed to be malignant were considered clinically important. The reference standard was renal mass protocol CT or MRI, ultrasound of definitively benign cysts or solid masses, single-phase contrast-enhanced CT or unenhanced MRI showing no growth or morphologic change for 5 years or more, or clinical follow-up 5 years or greater. A reference standard was available for 346 masses in 300 patients. The 95% CIs were calculated using the binomial exact method. RESULTS. Eligible masses were identified in 4.2% of patients (514/12,167; 95% CI, 3.9-4.6%). Of 346 masses with a reference standard, none were clinically important (0%; 95% CI, 0-0.9%). Mean mass size was 17 mm; 72% (248/346) measured 21-30 HU, and 28% (98/346) measured 31-39 HU. CONCLUSION. Incidental small homogeneous renal masses measuring 21-39 HU at portal venous phase CT are common and highly likely benign. CLINICAL IMPACT. The change in attenuation threshold signifying the need for additional imaging from greater than 20 HU to greater than 30 HU proposed by the Bosniak classification version 2019 is supported.

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome: Spectrum of imaging findings

PURPOSE

To retrospectively investigate the radiological presentations of HLRCC-associated renal tumors to facilitate accurate lesion characterization and compare these presentations with simple cysts and characteristics of other subtypes of renal cell carcinoma (RCC) as reported in the literature.

METHODS

The MRI and CT imaging characteristics of 39 pathologically confirmed lesions from 30 patients (20 male, 10 female) with HLRCC syndrome were evaluated by two radiologists. Patients had an average age at diagnosis of 43.8 ± 13.1 years. Lesion characteristics including laterality, homogeneity, diameter (cm), nodularity, septations, T1 and T2 signal intensity, enhancement, and restricted diffusion were recorded. Imaging characteristics of the lesions were further compared to characteristics of benign simple cysts surgically removed at the same time point.

RESULTS

The examined lesions had a mean diameter of 5.06 ± 3.80 cm, an average growth rate of 2.91 × 10^-3 cm/day and an estimated annual growth rate of 1.06 cm/year. 50% of lesions demonstrated nodularity, 65% were mostly T2-hyperintense, 83% demonstrated restricted diffusion in solid portions of the lesions, and 65% had well-defined margins. 76% of patients demonstrated extra-renal manifestations, 53% lymphadenopathy, and 43% distant metastasis.

CONCLUSIONS

Our analysis confirmed that while HLRCC-associated renal lesions demonstrate diversity in imaging presentations, the majority are unilateral and solitary, T2-hyperintense, heterogeneous with well-defined margins, and frequently demonstrate restricted diffusion and nodularity.

Contrast-enhanced ultrasound findings of adult renal cell carcinoma associated with Xp11.2 translocation/TFE3 gene fusion: comparison with clear cell renal cell carcinoma and papillary renal cell carcinoma

BACKGROUND

To investigate the contrast-enhanced ultrasound (CEUS) findings of renal cell carcinoma (RCC) associated with Xp11.2 translocation/TFE3 gene fusion (Xp11.2/TFE3) in adult patients by comparison with those of clear cell RCC (ccRCC) and papillary RCC (pRCC).

METHODS

In total, 110 patients (110 renal masses) who underwent CEUS examinations were enrolled in this study. The cases included 18 Xp11.2/TFE3 RCCs, 60 ccRCCs and 32 pRCCs. All masses were confirmed by operative pathology. The CEUS imaging data of these patients were retrospectively analysed by two readers. The conventional US and CEUS features of Xp11.2/TFE3 RCC were compared with those of ccRCC and pRCC.

RESULTS

The age of the patients with Xp11.2/TFE3 RCC ranged from 20 to 68 years, with a mean age of 38.3 ± 16.3 years and a slight female predominance. The weighted kappa value that interprets the concordance between the interobserver agreement of the US and CEUS features ranged from 0.61 to 0.89. On conventional US and CEUS imaging of Xp11.2/TFE3 RCCs, the tumours were hypoechoic (6/18, 33.3%), isoechoic (8/18, 44.4%), and hyperechoic (4/18, 22.2%). The cystic component was present in 5 cases (27.8%), calcification was present in 9 cases (50.0%), and colour flow signal was present in 7 cases (38.9%). Most cases showed simultaneous wash-in (11/18, 61.1%); the peak enhancement showed hypoenhancement (6/18, 33.3%), isoenhancement (10/18, 55.6%), and hyperenhancement (2/18, 11.1%); most cases exhibited heterogeneous enhancement (12/18, 66.7%) and fast- or simultaneous-out (16/18, 88.9%); and a pseudocapsule was present in 6 cases (33.3%). In the multivariate logistic regression analysis, calcification and lower peak enhancement were more likely to be present in Xp11.2/TFE3 RCC than in ccRCC (P < 0.05), and younger age and relatively high peak enhancement were more likely to be present in Xp11.2/TFE3 RCC than in pRCC (P < 0.05). The calcification combined peak enhancement model differentiated Xp11.2/TFE3 RCC from ccRCC, and the age combined peak enhancement model differentiated Xp11.2/TFE3 RCC from pRCC with an AUC, a sensitivity and a specificity of 0.896, 94.4% and 73.3% and 0.786, 50.0% and 100.0%, respectively.

CONCLUSIONS

The specific CEUS features combined with demographic information and clinical symptoms may be helpful for differentiating Xp11.2/TFE3 RCC from ccRCC and pRCC.

Computed Tomography Imaging Characteristics of Histologically Confirmed Papillary Renal Cell Carcinoma-Implications for Ancillary Imaging

Low-attenuation renal lesions on non-contrast computed tomography (CT) are often considered to be benign cysts without need for further imaging. However, the papillary subtype of renal cell carcinoma (RCC) may have similar radiographic characteristics. A single-center retrospective review was therefore performed to identify extirpated papillary RCC (pRCC) specimens with correlation made to preoperative tumor imaging characteristics. A total of 108 pRCC specimens were identified of which 84 (27 type I, 17 type 2, 40 unspecified) had CT imaging available for review. Non-contrast CT was available for 73 tumors with 16 (22%) demonstrating Hounsfield units (HU) measurements fewer than 20 at baseline without differences between papillary subtypes. Mean attenuation following contrast administration was similar between papillary subtypes (45 HU for type 1 pRCC and 49 HU for type 2). This study highlights that pathologically proven pRCC is a heterogeneous entity in terms of density on preoperative CT imaging. A non-contrast CT scan with HU fewer than 20 may not be an adequate evaluation for incidental renal masses, as over 1 in 5 pRCCs demonstrate lower attenuation than this cutoff. Further study is needed to identify the appropriate role of ancillary imaging in the workup of seemingly benign-appearing renal lesions.

Current Challenges in Diagnosis and Assessment of the Response of Locally Advanced and Metastatic Renal Cell Carcinoma

Locally advanced and metastatic renal cell carcinoma (RCC) present a specific set of challenges to the radiologist. The detection of metastatic disease is confounded by the ability of RCC to metastasize to virtually any part of the human body long after surgical resection of the primary tumor. This includes sites not commonly included in routine surveillance, which come to light after the patient becomes symptomatic. In the assessment of treatment response, the phenomenon of tumor heterogeneity, where clone selection through systemic therapy drives the growth of potentially more aggressive phenotypes, can result in oligoprogression despite overall disease control. Finally, advances in therapy have resulted in the development of immuno-oncologic agents that may result in changes that are not adequately evaluated with conventional size-based response criteria and may even be misinterpreted as progression. This article reviews the common challenges a radiologist may encounter in the evaluation of patients with locally advanced and metastatic RCC. ^©RSNA, 2019.

Differentiation of Papillary Renal Cell Carcinoma Subtypes on MRI: Qualitative and Texture Analysis

OBJECTIVE

The objective of this study was to determine whether quantitative texture analysis of MR images would improve the ability to distinguish papillary renal cell carcinoma (RCC) subtypes, compared with analysis of qualitative MRI features alone.

MATERIALS AND METHODS

A total of 47 pathologically proven papillary RCC tumors were retrospectively evaluated, with 31 (66%) classified as type 1 tumors and 16 (34%) classified as type 2 tumors. MR images were reviewed by two readers to determine tumor size, signal intensity, heterogeneity, enhancement pattern, margins, perilesional stranding, vein thrombosis, and metastasis. Quantitative texture analysis of gray-scale images was performed. A logistic regression was derived from qualitative and quantitative features. Model performance was compared with and without texture features.

RESULTS

The significant qualitative MR features noted were necrosis, enhancement appearance, perilesional stranding, and metastasis. A multivariable model based on qualitative features did not identify any factor as an independent predictor of a type 2 tumor. The logistic regression model for predicting papillary RCCs on the basis of qualitative and quantitative analysis identified probability of the 2D volumetric interpolated breath-hold examination (VIBE) sequence (AUC value, 0.87; 95% CI, 0.77-0.98) as an independent predictor of a type 2 tumor. No difference in the model AUC value was noted when texture features were included in the analysis; however, the model had increased sensitivity and an improved predictive value without loss of specificity.

CONCLUSION

The addition of texture analysis to analysis of conventional qualitative MRI features increased the probability of predicting a type 2 papillary RCC tumor, which may be clinically important.

Prevalence of Solid Tumors in Incidentally Detected Homogeneous Renal Masses Measuring > 20 HU on Portal Venous Phase CT

OBJECTIVE

The purpose of this study was to determine the prevalence of solid tumors in incidental homogeneous renal masses with attenuation greater than 20 HU on portal venous phase CT images.

MATERIALS AND METHODS

In this retrospective study, the records of patients with incidental indeterminate (> 20 HU) homogeneous renal masses on portal venous phase CT scans from September 11, 2007, through March 18, 2017, were identified. Adult patients were included if they had undergone follow-up ultrasound, contrast-enhanced MRI, multiphase contrast-enhanced CT, or pathologic analysis alone to confirm the solid or cystic nature of the lesion. A single ROI was placed in the center of the mass, and lesions were characterized as ≥ 50% exophytic, < 50% exophytic, or entirely surrounded by renal parenchyma.

RESULTS

There were 322 masses in 267 patients. The mean lesion size was 16.6 (SD, 9.8) mm (range, 9-45 mm). Lesions were ≥ 50% exophytic in 92 cases, < 50% exophytic in 111 cases, and completely surrounded by renal parenchyma in 119 cases. All nonsolid lesions were characterized as benign cysts. The numbers of solid lesions per total number of lesions in each attenuation group were: 20-30 HU (0/140), 30-40 HU (0/67), 40-50 HU (1/38), 50-60 HU (3/24), 60-70 HU (5/17), 70-80 HU (5/17), and > 80 HU (8/19). All 207 lesions in the 20- to 40-HU range were benign cysts with no solid lesions (0%; 95% CI, 0.0-1.4%).

CONCLUSION

Small homogeneous renal masses measuring 20-40 HU on portal venous phase CT images are highly likely to be benign cysts.

Can multiphase CT scan distinguish between papillary renal cell carcinoma type 1 and type 2?

OBJECTIVE

To investigate the utility of multiphase computed tomography (CT) and percutaneous renal mass biopsy (PRMB) in differentiating between papillary renal cell carcinoma (pRCC)-Type 1 and -Type 2, as emerging data have suggested differential enhancement patterns in different renal tumor histologies.

MATERIAL AND METHODS

Retrospective analysis of 51 patients (23 pRCC-Type 1/28 pRCC-Type 2) who underwent multiphase CT followed by surgery from July 2011 to April 2016 was performed. Data were analyzed between subgroups based on histology. Multiphase CT was analyzed for tumor size, and attenuation [Hounsfield Units (HU)]. Change in HU (ΔHU) was calculated between noncontrast (NC), corticomedullary (CM), nephrographic (N), and delayed (D) phases. Subset analysis was carried out on patients who underwent PRMB prior to surgery.

RESULTS

There was no difference in median tumor size (pRCC-Type 1 2.8 vs. pRCC-Type 2 2.6 cm, p=0.832). In addition to tumor size being similar between groups, distribution of tumor stages between groups was also similar (p=0.651). Greater proportion of high-grade tumors (III/IV) was noted in pRCC-Type 2 (42.9% vs. 8.7%) (p=0.011). There was no difference in HU values for NC (p=0.961), CM (p=0.118), N (p=0.277), and D (p=0.256) phases, and in ΔHU between CM-NC (p=0.278), N-NC (p=0.316), and D-NC (p=0.103). Thirteen patients underwent percutaneous biopsy, 11 of whom had diagnostic samples. Examination of 10/11 (90.9%) samples accurately predicted correct histology, and of 6/11 (54.5%) samples correctly identified high-vs. low-grade histology.

CONCLUSION

Our findings suggest substantial overlap of CT findings, despite pRCC-Type 2 having greater proportion of high-grade tumors. Utility of CT is limited in the differentiation between pRCC subtypes. Patients with suggested pRCC on CT imaging being considered for a non-extirpative strategy should undergo PRMB for risk stratification.

Imaging of Solid Renal Masses

The increase in serendipitous detection of solid renal masses on imaging has not resulted in a reduction in mortality from renal cell carcinoma. Consequently, efforts for improved lesion characterization have been pursued and incorporated into management algorithms for distinguishing clinically significant tumors from those with favorable histology or benign conditions. Although diagnostic imaging strategies have evolved for optimized lesion detection, distinction between benign tumors and both indolent and aggressive malignant neoplasms remain an important diagnostic challenge. Recent advances in cross-sectional imaging have expanded the role of these tests in the noninvasive characterization of solid renal tumors.

Imaging features of solid renal masses

The widespread use of abdominal imaging techniques has increased the detection of solid renal masses over the past years. Imaging plays a crucial role in the management and surveillance and in determining which lesions need treatment. The "classical angiomyolipoma" is the only benign solid renal mass that can be characterized with confidence by imaging through the detection of a fat-containing lesion without calcifications. There is a large overlap of imaging features between benign and malignant renal masses that often makes difficult a correct characterization of these lesions. In this review, we discuss the imaging features of the main solid renal masses that may suggest a likely benign diagnosis.

Type 1 papillary renal cell carcinoma: differentiation from Type 2 papillary RCC on multiphasic MDCT

PURPOSE

To investigate whether multiphasic MDCT enhancement can help differentiate type 1 papillary renal cell carcinoma (RCC) from type 2 papillary RCC.

METHODS

With IRB approval for this HIPAA-compliant retrospective study, we derived a cohort of 36 type 1 papillary RCCs and 33 type 2 papillary RCCs with preoperative multiphasic MDCT with up to four phases (unenhanced, corticomedullary, nephrographic, and excretory) from 2000 to 2013. Following segmentation, a computer-assisted detection (CAD) algorithm selected a 0.5 cm-diameter region of maximal attenuation within each lesion in each phase; a 0.5 cm-diameter region of interest was manually placed on uninvolved renal cortex in each phase. The relative attenuation of each lesion was calculated as [(Lesion attenuation-cortex attenuation)/cortex attenuation] × 100. Absolute and relative attenuation values were compared using Mann-Whitney tests with Bonferroni correction for multiple comparisons.

RESULTS

Relative excretory phase attenuation of type 2 papillary RCCs was significantly greater than that of type 1 papillary RCCs (2.0 vs. -18.3, p = 0.005). Relative excretory phase attenuation differentiated type 1 papillary RCCs from type 2 papillary RCCs with an accuracy of 73% (36/49), sensitivity of 87% (26/30), positive predictive value of 74% (26/35), and negative predictive value of 71% (10/14).

CONCLUSION

Multiphasic MDCT enhancement may assist in differentiating type 1 papillary RCCs from type 2 papillary RCCs, if prospectively validated.

Imaging of Solid Renal Masses

Detection of solid renal masses has increased, although it has not resulted in significant mortality reduction from renal cell carcinoma. Efforts for improved lesion characterization have been pursued and incorporated in management algorithms, in order to distinguish clinically significant tumors from favorable or benign conditions. Concurrently, imaging methods have produced evidence supporting their role as useful tools not only in lesion detection but also characterization. In addition, newer modalities, such as contrast-enhanced ultrasonography, and advanced applications of MR imaging, are being investigated. This article reviews the current role of different imaging methods in the characterization of solid renal masses.

Correlating Preoperative Imaging with Histologic Subtypes of Renal Cell Carcinoma and Common Mimickers

Renal cell carcinoma (RCC) consists of distinct subtypes that have unique pathologic and imaging features as well as specific cytogenetic and molecular characteristics. As the prognosis and therapeutic strategies may differ for each subtype, correlation of the preoperative imaging with the pathologic findings is of great clinical relevance. In addition, differentiation of RCC from benign entities is ideal in order to prevent overtreatment. However, a noninvasive diagnosis with imaging alone is not always straightforward due to the overlapping appearance of RCC with benign lesions such as fat-poor angiomyolipoma and oncocytoma. With new imaging modalities, there have been significant improvements in correlating preoperative imaging with pathologic characteristics. These new discoveries are able to aid in a more specific, noninvasive, diagnosis that in turn helps direct patient management.

Dynamic Contrast-Enhanced CT Characterization of Xp11.2 Translocation/TFE3 Gene Fusions versus Papillary Renal Cell Carcinomas

PURPOSE

To compare the differences of CT characteristics between renal cell carcinomas (RCCs) associated with Xp11.2 translocation/TFE3 gene fusions (Xp11.2 RCCs) and papillary cell renal cell carcinomas (PRCCs).

METHODS

CT images and clinical records of 64 patients (25 Xp11.2 RCCs, 15 type 1 and 24 type 2 PRCCs) were analyzed and compared retrospectively.

RESULTS

Xp11.2 RCC more frequently affected young (30.7 ± 8.7 years) women (16/25, 64%) with gross hematuria (12/25, 48%), while PRCC more frequently involved middle-aged (54.8 ± 11.1 years) men (28/39, 71.8%) asymptomatically. Xp11.2 RCC tended to be heterogeneous density with some showing circular calcification. Lesion sizes of Xp11.2 RCC (5.4 ± 2.2 cm) and type 2 PRCC (5.7 ± 2.5 cm) were significantly larger than that of type 1 PRCC (3.8 ± 1.8 cm). Xp11.2 RCC contained more cystic components (22/25, 88%) than type 1 PRCC (all solid) and type 2 PRCC (9/24, 36.0%). Type 1 PRCC (13/15, 86.7%) and Xp11.2 RCC (21/25, 84.0%) showed more clear boundary than type 2 PRCC (12/24, 50.0%).

CONCLUSION

CT features including diameter, boundary, attenuation, nature, and circular calcification of the tumor, combined with demographic information and symptoms, may be useful to differentiate Xp11.2 RCC from different subtypes of PRCC.

CT Hounsfield numbers of soft tissues on unenhanced abdominal CT scans: variability between two different manufacturers' MDCT scanners

OBJECTIVE

The purpose of this study is to determine whether Hounsfield numbers of soft tissues on unenhanced abdominal CT of the same patient vary on repeat scans done on two different manufacturers' MDCT scanners.

MATERIALS AND METHODS

A database search was performed to identify patients older than 18 years who underwent unenhanced CT of the abdomen and pelvis performed both on a Volume CT (GE Healthcare) and a Definition AS Plus (Siemens Healthcare) 64-MDCT scanner within 12 months of each other. After excluding those patients for whom Hounsfield unit measurements would be affected by mitigating factors, 48 patients (mean age, 58.8 years) were identified. Hounsfield unit measurements were obtained in nine different soft-tissue anatomic locations on each scan, and the location of these sites was kept identical on each scan pair. Data were analyzed to evaluate Hounsfield unit differences between these scanners.

RESULTS

In general, there was a low consistency in the Hounsfield unit measurements for each of these sites on scans obtained by the two scanners, with the subcutaneous fat in the left posterolateral flank showing the lowest correlation (intraclass correlation coefficient, 0.198). There were differences in the Hounsfield unit measurements obtained in all anatomic sites on scans obtained by both scanners. Mean Hounsfield unit measurements obtained on the Definition AS Plus scanner were lower than those obtained on the Volume CT scanner, with the intriguing exception of the anterior midline subcutaneous fat Hounsfield unit measurements, which were higher on the Definition AS Plus scanner. All differences were statistically significant (p < 0.05).

CONCLUSION

Hounsfield unit measurements for unenhanced abdominal soft tissues of the same patient vary between scanners of two common MDCT manufacturers.

Tumor grade of clear cell renal cell carcinoma assessed by contrast-enhanced computed tomography

The purpose of this study was to clarify the association between CT findings and Fuhrman grade of clear cell renal cell carcinoma (ccRCC). The study group consisted of 214 surgically proven ccRCC in 214 patients. Contrast-enhanced CT studies were retrospectively assessed for tumor size, cystic versus solid, calcification, heterogeneity of lesions, percentage of non-enhancing (necrotic) areas, and growth pattern. CT findings and Fuhrman grade were compared. Nineteen of 22 (86.4%) cystic ccRCC were low grade (Fuhrman grades 1-2). There was no significant correlation between tumor size and grade in cystic ccRCC (P = 0.43). In predominantly solid ccRCC, there was significant correlation between tumor size and grade (P < 0.0001). Thirty-eight of 43 (88.4%) infiltrative ccRCC were high grade (Fuhrman grades 3-4). Logistic regression showed tumor size and infiltrative growth were significantly associated with grades 3-4 (P = 0.00083 and P = 0.0059). Cystic ccRCC tends to be low grade. Infiltrative growth and larger tumor size may increase the likelihood of high grade ccRCC.

Spontaneous rupture of the kidney affected by multifocal papillary renal cell carcinoma

Papillary renal cell carcinoma (pRCC) represents the second most common type of malignant renal epithelial tumor (represents the 10% of the kidney's carcinoma) and can be subclassified in the basophile type I and eosinophile type II. We report a clinical case of spontaneous rupture of the kidney affected by multifocal (42 tumors foci) pRCC in a young man 53 years old, without showing earlier specific cancer signs and symptoms. Prognosis for type I pRCC is better than type II pRCC, but it is anyway related to the tumoral grade, to the tumoral stage and to the diagnostic precocity. Signs and symptoms are very similar to those characterizing the more frequent clear cell carcinoma. Nevertheless in the 40% of the cases the lesion is asymptomatic. To our knowledge, this is the first case of spontaneous rupture of the kidney affected by multifocal pRCC in literature without showing earlier specific cancer signs and symptoms.

MRI phenotype in renal cancer: is it clinically relevant?

Renal cell carcinoma (RCC) is most commonly diagnosed as an incidental finding on cross-sectional imaging and represents a significant clinical challenge. Although most patients have a surgically curable lesion at the time of diagnosis, the variability in the biologic behavior of the different histologic subtypes and tumor grade of RCC, together with the increasing array of management options, creates uncertainty for the optimal clinical approach to individual patients. State-of-the-art magnetic resonance imaging (MRI) provides a comprehensive assessment of renal lesions that includes multiple forms of tissue contrast as well as functional parameters, which in turn provides information that helps to address this dilemma. In this article, we review this evolving and increasingly comprehensive role of MRI in the detection, characterization, perioperative evaluation, and assessment of the treatment response of renal neoplasms. We emphasize the ability of the imaging "phenotype" of renal masses on MRI to help predict the histologic subtype, grade, and clinical behavior of RCC.

Pretreatment differentiation of renal cell carcinoma subtypes by CT: the influence of different tumor enhancement measurement approaches

PURPOSE

We conducted a retrospective study to evaluate the influence of different tumor enhancement measurement approaches on the ability of computed tomography (CT) to differentiate between solid forms of clear cell renal cell carcinoma (RCC), other RCC histologic subtypes and oncocytomas. Different RCC subtypes have a diverse range of malignant potential; consequently, the information about RCC subtype obtained using minimally invasive imaging method before the treatment could allow the more accurate therapy planning. Differentiation of ccRCCs from oncocytomas is important because oncocytomas are usually benign tumors which could be treated conservatively.

METHODS

CT images of 113 patients with 118 solid renal tumors were evaluated. The imaging protocol consisted pre-contrast and post-contrast images during the arterial and nephrographic phases. Renal tumor attenuation values were measured using region of interest covering as much of the solid enhancing tumor tissue as possible. Tumor attenuation values and tumor enhancement ratios were correlated with histologic subtype. One hundred of tumors were diagnosed as clear cell RCC, nine as non-clear cell RCC and nine as oncocytoma.

RESULTS

Tumor attenuation values of >74 HU on the arterial phase scans significantly correlated with clear cell RCC (Az 0.73). The tumor-to-aorta enhancement ratios calculated on tumor attenuation values measured on the arterial phase scans had a cutoff value of >0.29, which significantly correlated with clear cell RCC (Az 0.79). All ROC curves for differentiating the clear cell RCC from oncocytomas have area under the curve too small (0.5 or less) to have chose cutoff value with sensitivity and specificity that could be applied in clinical work.

CONCLUSION

Enhancement measurements of renal carcinomas on CT images in the arterial phase can be used as an auxiliary method in the pretreatment differentiation of solid forms of the most frequent RCC subtypes in patients not suitable for core biopsy but who are suitable for minimally invasive treatment methods and/or targeted therapy.

Differentiation of papillary renal cell carcinoma subtypes on CT and MRI

OBJECTIVE

The objective of our study was to determine the frequency of atypical papillary renal cell carcinomas (RCCs) and identify imaging differences between type 1 and type 2 papillary RCCs once atypical papillary RCC tumors have been excluded.

MATERIALS AND METHODS

Eighty-two papillary RCC tumors were classified at pathology as type 1, type 2, or atypical. The CT and MRI examinations of these tumors were reviewed. Imaging features such as tumor size, margins, heterogeneity, and enhancement were assessed and the findings in type 1 and type 2 tumors were compared.

RESULTS

There were 43 type 1 and 13 type 2 tumors. Atypical histologic features (i.e., tumors containing both type 1 and type 2 components, clear cells, or components with atypically high nuclear grade [in type 1 tumors] or low nuclear grade [in type 2 tumors]) were seen in 26 tumors. On CT, type 2 tumors more commonly had infiltrative margins (p = 0.05) and were more likely to have calcifications (p = 0.04) than type 1 tumors, although these features were seen in all tumor types. Type 2 tumors were also more heterogeneous than type 1 tumors (p = 0.04). On CT, 11 papillary RCCs showed enhancement of less than 20 HU, seven of which showed enhancement of less than 10 HU. On MRI, all tumors showed enhancement on subtraction images.

CONCLUSION

Nearly one third of papillary RCCs in our patient population had atypical features at histology. On CT and MRI, there are some significant differences in imaging features between type 1 and type 2 tumors; however, substantial overlap precludes categorization on a per-patient basis. On CT, many papillary RCCs do not enhance, indicating that assessment of enhancement alone is insufficient for differentiating papillary RCCs from hyperdense cysts.

A type 2 papillary renal cell carcinoma presenting as an intracystic necrotic lesion: A case report

Papillary renal carcinoma (papillary RCC) is a histological subtype of the renal carcinoma, which in turn, has two morphological subtypes that correlate with prognosis. The present study reported an unexpected finding of type 2 papillary renal cell carcinoma (papillary RCC) presenting intracystic necrosis cavity. A cystic renal lesion was identified incidentally in a 66-year-old man during an abdominal computed tomography (CT) scan performed for the evaluation of a gastrointestinal stromal tumor. Subsequent contrast material-enhanced CT scan and magnetic resonance imaging (MRI) examination labeled the mass as category III degree on the basis of the Bosniak classification scheme. Surgical exploration by laparoscopic radical nephrectomy was performed to determine the diagnosis. Definitive pathological study confirmed a type 2 papillary RCC with an intracystic necrosis cavity. To the best of our knowledge, this case demonstrated for the first time a cavity within a papillary RCC, supporting the hypothesis that type 2 papillary RCC could develop cavity avascular necrosis during its cystic degeneration.

Prognostic implications of the magnetic resonance imaging appearance in papillary renal cell carcinoma

OBJECTIVE

To evaluate the prognostic implications of the MRI appearance and pathological features of papillary renal cell carcinoma (pRCC).

METHODS

A total of 128 pRCC in 115 patients who underwent preoperative MRI were characterised in terms of pathological type (type 1 vs. type 2), MRI appearance (focal vs. infiltrative) and additional MRI features. Patients were classified on the basis of the presence or absence of metastatic disease.

RESULTS

There were 65 focal type 1, 54 focal type 2 and 9 infiltrative pRCC. All infiltrative pRCC were of histopathological type 2. Renal vein thrombus was present in 89 % of infiltrative pRCC and no cases of focal pRCC. Metastatic disease was observed in 3.7 % of focal type 1, 7.5 % of focal type 2 and 75.0 % of infiltrative type 2 pRCC. Infiltrative MRI appearance was a significant predictor of metastatic disease, independent of pathological type, size and T stage (P ≤ 0.020). Among focal pRCC on MRI, pathological type 2 was not a significant predictor of metastatic disease (P = 0.648). No combination of features achieved significantly greater accuracy for predicting metastatic disease than renal vein thrombus alone (P > 0.5).

CONCLUSION

Infiltrative MRI appearance and renal vein thrombus identify a subset of pathological type 2 pRCC at a significantly increased risk of metastatic disease.

Papillary renal cell carcinoma: radiologic-pathologic correlation and spectrum of disease

Papillary renal cell carcinoma (pRCC) is the second most common type of renal cell carcinoma (RCC). pRCC has unique imaging and clinical features that may allow differentiation from clear cell RCC (cRCC). There have been significant advances in our knowledge of the natural history and treatment of pRCC, with data suggesting that it may be best to manage pRCC differently from the other subtypes of RCC. At contrast material-enhanced computed tomography, pRCC enhances less than does cRCC in all phases of contrast-enhanced imaging. The difference in the degree of enhancement between pRCC and cRCC is due to differences in their intratumoral vascularity. In general, if a heterogeneous mass enhances to a degree similar to that manifested by the renal cortex, it is likely to be a cRCC. A mass that enhances to a lesser degree is likely to be a non-clear cell RCC. It is common for metastatic lesions from pRCC to show enhancement characteristics similar to those of the primary tumor and be hypovascular.