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

Multimodality Imaging Features of Papillary Renal Cell Carcinoma

Objectives: To describe the US, CEUS, CT, and MRI features of papillary renal cell carcinoma (PRCC) and to underline the imaging characteristics that are helpful in the differential diagnosis. Methods: Patients with histologically proven papillary renal cell carcinoma who underwent at least two imaging examinations (US, CEUS, CT, and MRI) were included in the study. Tumor size, homogeneity, morphology, perilesional stranding, contrast enhancement locoregional extension were assessed. A comparison and the characteristics of the imaging features for each imaging modality were analyzed. Results: A total of 27 patients with an histologically confirmed diagnosis of PRCC were included in the study. US was highly accurate in distinguishing solid masses from cystic masses, supporting the differential diagnosis of PRCC, as well as in patients with a poor representation of the solid component. CEUS significantly increased diagnostic accuracy in delineating the solid intralesional component. Furthermore, when using CEUS, in the arterial phase, PRCC exhibited hypo-enhancement, and in the late phase it showed an inhomogeneous and delayed wash-out compared with the surrounding renal parenchyma. At MRI, PRCC showed a marked restiction of DWI and was hypointense in the T2-weighted compared to the renal parenchyma. Conclusions: In our study, the characteristic hypodensity and hypoenhancement of PRCC make CT the weakest method of their recognition, while US/CEUS and MRI are necessary to reach a definitive diagnosis. Knowledge of the appearance of PRCC can support an early diagnosis and prompt management, and radiologists should be aware that PRCC, when detected using CT, may resemble spurious non-septate renal cyst.

Diagnostic performance of contrast enhancement to differentiate benign and malignant renal lesions in CT and MRI: a systematic review and meta-analysis of diagnostic test accuracy (DTA) studies

OBJECTIVE

To perform a systematic review and meta-analysis of the diagnostic performance of contrast enhancement to differentiate benign and malignant renal lesions using CT and MRI.

MATERIAL AND METHODS

A systematic literature search of databases was performed between January 1, 1980 and September 26, 2022. We included studies reporting the accuracy of CE thresholds on CT and MRI indeterminate renal lesions, with pathologic examination and follow-up as the reference standard. Studies meeting the inclusion criteria underwent quality assessment with the Cochrane recommendation for diagnostic accuracy study Quality Assessment 2. We excluded studies with high risk of bias. Summary estimates of diagnostic performance were obtained with the bivariate Bayesian model for CT and MRI. Effects of different thresholds and index test modalities were investigated through subgroup analysis.

RESULTS

Eleven studies (1372 patients) using CT and six studies (218 patients) using MRI were included. Of the eleven studies, 15 parts from 9 studies were considered for the CT meta-analysis, and 6 parts from 3 studies for the MRI meta-analysis. Diagnostic performance meta-analysis on enhancement found a 96% summary sensitivity (95% CI 92, 98) and a 92% summary specificity (95% CI 85, 96) in 2056 renal lesions for CT; and 82% summary sensitivity (95% CI 65, 89) and an 89% summary specificity (95% CI 77, 95) in 634 lesions for MRI.

CONCLUSION

CT and MRI have high accuracy to determine enhancement and classify renal lesions, and both modalities can be used with confidence for this purpose. There are still some controversies about the optimal thresholds. Future research should evaluate outcomes and decision-making pathways to determine whether basing clinical decisions on a specific threshold on CT and MRI would do more harm than good.

Molecular imaging of renal cell carcinomas: ready for prime time

The clinical diagnosis of renal cell carcinoma (RCC) is constantly evolving. Diagnostic imaging of RCC relying on enhanced computed tomography (CT) and magnetic resonance imaging (MRI) is commonly used for renal mass characterization and assessment of tumour thrombosis, whereas pathology is the gold standard for establishing diagnosis. However, molecular imaging is rapidly improving the clinical management of RCC, particularly clear-cell RCC. Molecular imaging aids in the non-invasive visualization and characterization of specific biomarkers such as carbonic anhydrase IX and CD70 within the tumours, which help to assess tumour heterogeneity and status. Target-specific molecular imaging of RCCs will substantially improve the diagnostic landscape of RCC and will further facilitate clinical decision-making regarding initial staging and re-staging, monitoring of recurrence and metastasis, patient stratification and selection, and the prediction and evaluation of treatment responses.

Localized abdominal wall metastasis of papillary renal cell carcinoma: a case report

Introduction

Papillary renal cell carcinoma accounts for one tenth of all renal cell carcinomas. Compared to other renal cell carcinoma subtypes, it is more often localized at the time of diagnosis and rarely metastasizes to the skin. There are no previously reported cases of cutaneous papillary renal cell carcinoma localized to the abdominal wall which we present here.

Case presentation

A 77 year-old female with multiple previous cancers, including a stage 1 left papillary renal cell carcinoma, treated with partial nephrectomy 32 months prior to presentation, was found to have a left upper abdominal wall mass on interval screening computed tomography. Fine needle aspiration was performed, obtaining limited tissue, followed by incisional biopsy. Histology and immunohistochemistry were consistent with renal cell carcinoma. She underwent operative excision of the abdominal wall mass with reconstruction using mesh and left posterior rectus fascial release. Histology and immunohistochemistry of the operative specimen reconfirmed the diagnosis of cutaneous metastasis of renal cell carcinoma. She was treated with adjuvant pembrolizumab and has no existing evidence of disease.

Conclusions

Papillary renal cell carcinoma metastasized to the skin is uncommon, especially when localized to the abdominal wall without any other sites of metastases. Metastasis should be on the differential diagnosis when evaluating newly identified abdominal masses in patients with a history of papillary renal cell carcinoma. When localized, abdominal wall metastasis of papillary renal cell carcinoma can be effectively treated with resection and reconstruction, followed by systemic therapy when indicated.

[2022 WHO classification of renal cell carcinomas: Focus on papillary renal cell carcinoma]

Renal cell carcinomas (RCC) represent a group of heterogeneous tumors whose classification has greatly evolved since 1981. The latest update in 2022 classifies all renal cell carcinomas into six categories according to their morphology or the detection of specific molecular alterations. Molecular disassembly of renal cell carcinomas with papillary features has enabled the identification of new entities characterized by a specific molecular alteration, such as Fumarate Hydratase (FH) deficient RCC, TFE3-rearranged RCC or TFEB-altered RCC. This new classification allows for a more accurate diagnosis but requires a thorough knowledge of the genomic alterations to search for with immunohistochemical or molecular biology techniques. According to the new WHO 2022 classification, papillary renal cell carcinoma (PRC) type 1 or type 2 classification is no longer recommended. A classification based on nucleolar ISUP grade must be preferred: low-grade PRC (ISUP 1-2) or high-grade PRC (ISUP 3-4). The other prognostic factors remain the same: the pTNM stage, lymphovascular invasion, and the presence or absence of dedifferentiated areas referring to sarcomatoid or rhabdoid features. Of note, the presence of necrosis is not currently recognized as a poor prognostic element for this type of carcinoma. The diagnosis of high-grade PRC is from now on a diagnosis of exclusion. It can only be sustained after having ruled out TFE3-rearranged RCC, TFEB-altered RCC, and FH-deficient RCC. For clinicians, the diagnosis of PRC implies suggesting an oncogenetic consultation to screen for an associated genetic tumor syndrome regardless of the patient's age.

World Health Organization 2022 Classification Update: Radiologic and Pathologic Features of Papillary Renal Cell Carcinomas

RATIONALE AND OBJECTIVES

To describe imaging and pathology features of newly defined papillary renal cell carcinoma (pRCC) based on the WHO 2022 update.

MATERIALS AND METHODS

This retrospective study included 87 patients with 93 pathologically proven papillary renal cell carcinomas who underwent pre-treatment renal mass protocol CT or MRI. Baseline and post-treatment follow-up imaging was evaluated by two radiologists systematically based on established lexicon.

RESULTS

At pathology, 63 (68%) were grade 1-2, 29 (31%) were grade 3-4, and 1 (%) was unreported. At surgical pathology, 84 (90%) were localized (≤pT2b), 5 (5%) were pT3a, and none were ≥pT3b; 4 (4%) had unknown pT stage (core biopsies). 33 (35%) had necrosis and 39 (41%) had hemorrhage. None had sarcomatoid or rhabdoid differentiation. At imaging, 73 (83%) were solid and 16 (17%) were cystic. Of 16 cystic masses, four were Bosniak class IIF (three were heterogeneously T1 hyperintense) and 12 were class IV. All were well-circumscribed. 92 (99%) were hypovascular. Median follow-up for 74 patients was 30 months (IQR 12-56). One untreated patient had non-regional nodal metastasis at presentation, and one patient had metastasis to lymph nodes and bones after surgery, but the patient had unresected renal masses elsewhere without pathology. Otherwise, no recurrence or metastases were detected.

CONCLUSION

Most pRCCs present as a hypovascular, circumscribed, solid renal mass. A few pRCCs present as the newly defined Bosniak class IIF subtype. Our results can form the basis of a non-invasive, likelihood score to identify this relatively indolent pathology in the era of virtual biopsy and active surveillance.

Primary extrarenal papillary type II renal cell carcinoma presenting as a pelvic mass: a case report and review of the literature

We report a case of a 57 years old woman with a solitary mass located in the pelvis diagnosed as an extrarenal papillary renal cell carcinoma, in the absence of a primary renal cancer. The diagnosis was based on cytomorphological features and further confirmed by immunochemistry findings following surgical excision. The hypothesis of a tumor developing in a supernumerary or ectopic kidney was excluded, since no normal renal tissue could be identified in the specimen and in the preoperative computed tomography and MRI images.

Papillary Renal Cell Carcinoma in Transplanted Kidney and Xp11.2 Translocation/Transcription Factor E3-Rearranged Renal Cell Carcinoma in the Native Kidney: A Case Report

Concomitant renal cell carcinomas (RCC) of both native and allograft kidneys are extremely rare, and only a few cases have been reported in the available English literature. A particularly rare variant within the adult population is the Xp11.2 translocation/transcription factor E3 (TFE3)-rearranged RCC. Although few case reports of TFE3-rearranged RCC have been reported in children who underwent kidney transplantation (KT), no case of adults with TFE3-rearranged RCC following KT has been reported. Herein, we presented the radiological and pathological findings of a rare metachronous papillary RCC in the allograft kidney and TFE3-rearranged RCC in the native kidney. The TFE3-rearranged RCC in the native kidney exhibited slow expansion in size over five years. Radiologically, it appeared as a slightly enhanced, lobulated mass on contrast-enhanced CT. MRI revealed high signal intensity on T1-weighted images and low signal intensity on T2-weighted images.

68 Ga-FAPI-04 PET/CT in a Small Sarcomatoid Renal Cell Carcinoma With Widespread Metastases

ABSTRACT

Sarcomatoid renal cell carcinoma is an uncommon high-grade malignancy with poor prognosis. We describe 68 Ga-FAPI-04 PET/CT findings in a patient with a small (1.8 cm in the maximum diameter) sarcomatoid clear cell renal cell carcinoma with widespread metastatic disease. Both the primary renal tumor and its metastases in bones, lymph nodes, adrenals, and liver showed increased 68 Ga-FAPI-04 uptake. The primary renal tumor showed hypovascularity on contrast-enhanced CT, mimicking papillary renal cell carcinoma. This case indicates FAPI PET/CT may be useful for detecting and staging of this unusual malignancy.

Magnetic Resonance Imaging Virtual Biopsy of Common Solid Renal Masses-A Pictorial Review

ABSTRACT

The expanded application of radiologic imaging resulted in an increased incidence of renal masses in the recent decade. Clinically, it is difficult to determine the malignant potential of the renal masses, thus resulting in complex management. Image-guided biopsies are the ongoing standard of care to identify molecular variance but are limited by tumor accessibility and heterogeneity. With the evolving importance of individualized cancer therapies, radiomics has displayed promising results in the identification of tumoral mutation status on routine imaging. This article discusses how magnetic resonance imaging features can guide a radiologist toward identifying renal mass characteristics.

Imaging Findings of a Renomedullary Interstitial Cell Tumor: A Case Report

Introduction: Renomedullary interstitial cell tumors are benign tumors of renal medulla. They are usually asymptomatic, and preoperative diagnosis based on radiological findings is challenging. Therefore, in most clinical situations, nephrectomy is ultimately performed for differential diagnosis. Case Presentation: A 54-year-old woman presented to our hospital with hematuria. An incidental mass in the left kidney was detected on abdominal computed tomography (CT) scan. The mass showed iso-attenuation to renal parenchyma in the pre-contrast image and hypo-attenuation in the portal venous phase; however, some enhancement was observed in the central portion of the mass. Based on contrast-enhanced ultrasonography (CEUS) after one year, a slight septum-like enhancement was observed in the central portion of the mass in the venous phase. In dynamic contrast-enhanced T1- and T2-weighted magnetic resonance images (MRI), the mass showed a low signal intensity, and delayed persistent enhancement was observed in 10- and 15-minute delayed phases. The mass was finally diagnosed as a renomedullary interstitial cell tumor. Conclusion: The imaging findings of renomedullary interstitial tumors included a low-signal-intensity mass of renal medulla on T1- and T2-weighted MRI and delayed enhancement on CEUS and dynamic MRI.

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.

Importance of tumor subtypes in cancer imaging

Cancer therapy has evolved from being broadly directed towards tumor types, to highly specific treatment protocols that target individual molecular subtypes of tumors. With the ever-increasing data on imaging characteristics of tumor subtypes and advancements in imaging techniques, it is now often possible for radiologists to differentiate tumor subtypes on imaging. Armed with this knowledge, radiologists may be able to provide specific information that can obviate the need for invasive methods to identify tumor subtypes. Different tumor subtypes also differ in their patterns of metastatic spread. Awareness of these differences can direct radiologists to relevant anatomical sites to screen for early metastases that may otherwise be difficult to detect during cursory inspection. Likewise, this knowledge will help radiologists to interpret indeterminate findings in a more specific manner.

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Tumor subtypes can be identified based on their different imaging characteristics.

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Awareness of tumor subtype can help radiologists chose the appropriate modality for additional imaging workup.

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Awareness of differences in metastatic pattern between tumor subtypes can be helpful to identify early metastases.

Giant Polycystic Papillary Renal Cell Carcinoma: A Case Report and Literature Review

Introduction

Giant, cystic renal tumors are generally considered relatively contraindicated for laparoscopic surgery. We report on a 19-year-old male, where polycystic lesions in the left kidney were accidentally noted by enhanced computed tomography (CT) by focusing on the diagnostic, clinical, and surgery to the patient.

Case Report

Enhanced CT scan revealed solid component in multiple cystic lesions of Bosniak IV, which was enhanced after injection of contrast agent and the left kidney lost normal profile and enlarged with maximal diameter more than 18cm. Positron emission tomography-computed tomography (PET-CT) showed SUVmax 4.8 of the lesion and suggested malignant disease. A retroperitoneal laparoscopic radical left nephrectomy was performed successfully without cyst burst and the lesion was 17×17×18 cm in size. Pathological examination revealed that the lesions were consistent with papillary renal cell carcinoma (type 2, WHO grade II), no renal capsule invasion, no renal pelvis and renal sinus fat involvement, no abnormality in ureter and renal arteriovenous end, no abnormality in a few adrenal tissues, chronic inflammation of hilar lymph nodes (0/1). After surgery, no specific treatment was initiated and at a follow-up visit 1 year after surgery, no local recurrence or metastasis was found.

Conclusion

It is the largest cystic renal cell carcinoma that has ever been reported for laparoscopic resection. The selection of surgery for giant cystic renal cell carcinoma should be individualized. Retroperitoneal laparoscopy may be an option for such lesions.

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.

Comprehensive Analysis of Pyroptosis-Related Genes and Tumor Microenvironment Infiltration Characterization in Papillary Renal Cell Carcinoma

Background: Immunotherapy has emerged as an important technique for treating a variety of cancers. The dynamic interplay between tumor cells and invading lymphocytes in the tumor microenvironment is responsible for the good response to immunotherapy (TME). Pyroptosis, or inflammation-induced cell death, is closely linked to a number of cancers. However, in papillary renal cell carcinoma (KIRP), the association between pyroptosis and clinical prognosis, immune cell infiltration, and immunotherapy impact remains unknown.

Methods: We carefully investigated the link between pyroptosis and tumor growth, prognosis, and immune cell infiltration by evaluating 52 pyroptosis-related genes. The PRG score was utilized to measure a single tumor patient’s pyroptosis pattern. After that, we looked at how well these values predicted prognoses and therapy responses in KIRP.

Results: We discovered that PRG differences between subgroups were linked to clinical and pathological aspects, prognosis, and TME in two separate genetic subtypes. After that, a PRG score for estimating overall survival (OS) was developed, and its predictive potential in KIRP patients was confirmed. As a result, we developed a very precise nomogram to improve the PRG score’s clinical usefulness. A low PRG score, which is determined by mutation load and immune activation, suggests a good chance of survival. Furthermore, the PRG score was linked to chemotherapeutic drug sensitivity in a substantial way.

Conclusions: The possible functions of PRGs in the TME, clinical and pathological characteristics, and prognosis were established in our thorough investigation of PRGs in KIRP. These results might help us better understand PRGs in KIRP and offer a new avenue for prognostic evaluation and the development of more effective immunotherapy treatments.

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.

Application of contrast-enhanced ultrasound in the pathological grading and prognosis prediction of hepatocellular carcinoma

BACKGROUND

To explore the clinical application value of contrast-enhanced ultrasound (CEUS) in the pathological grading and prognosis prediction of hepatocellular carcinoma (HCC).

METHODS

A retrospective analysis was performed of 128 patients with primary HCC who underwent CEUS examination in our hospital from January 2017 to June 2020. Patients were divided into three groups: highly-differentiated group, moderately-differentiated group, and poorly-differentiated group. Quantitative analysis of the relationships between the rise time (RT), time to peak (TTP), mean transit time (mTT), intensity maximum (Imax), enhancement rate, and pathological grade of CEUS was performed. In addition, the follow-up patients were divided into a recurrence group and non-recurrence group, and the relationships between RT, TTP, mTT, Imax, and enhancement rate of CEUS were analyzed.

RESULTS

Among the 128 patients, 23 were highly-differentiated, 63 were moderately-differentiated, and 42 were poorly-differentiated. In addition, there were 31 patients in the recurrence group and 97 patients in the non-recurrence group. RT, TTP, and enhancement rate had significant differences in the highly-differentiated, moderately-differentiated, and poorly-differentiated groups. At the same time, RT and TTP were positively correlated with the differentiation degree, while the enhancement rate was negatively correlated with the differentiation degree. Furthermore, RT, TTP, and enhancement rate were statistically significant for the diagnosis of HCC with high, moderate, and poor differentiation, among which RT had the highest diagnostic accuracy. In the recurrence group, RT, TTP, and Imax were lower than those in the non-recurrence group, and the enhancement rate was greater than that in the non-recurrence group. Moreover, low levels of RT, TTP, and Imax along with positive microvascular invasion (MVI) and poor differentiation were risk factors for HCC recurrence, and there was no significant relationship between the average tumor diameter and HCC recurrence.

CONCLUSIONS

CEUS can significantly show the differences between the RT, TTP, and enhancement rate of HCC across different levels of differentiation. It can also predict whether the disease will relapse. Moreover, low levels of RT, TTP, and Imax as well as positive MVI and poor differentiation can cause the recurrence of HCC.

PTEN Hamartoma Tumor Syndrome/Cowden Syndrome: Genomics, Oncogenesis, and Imaging Review for Associated Lesions and Malignancy

Simple Summary

In this manuscript, we present the associated imaging findings and imaging screening recommendations. Knowledge of the types of cancers commonly seen in Cowden syndrome and their imaging findings can aid in early tumor recognition during cancer screening to help ensure near-normal life spans in Cowden syndrome patients.

Abstract

PTEN hamartoma tumor syndrome/Cowden syndrome (CS) is a rare autosomal dominant syndrome containing a germline PTEN mutation that leads to the development of multisystem hamartomas and oncogenesis. Benign tumors such as Lhermitte–Duclos disease and malignant tumors involving the breast, thyroid, kidneys, and uterus are seen in CS. Radiologists have an integral role in the comanagement of CS patients. We present the associated imaging findings and imaging screening recommendations. Knowledge of the types of cancers commonly seen in CS and their imaging findings can aid in early tumor recognition during cancer screening to help ensure near-normal life spans in CS patients.

Papillary renal cell carcinoma: Review

Kidney cancer is the 13th most common malignancy globally, and the incidence is rising. Papillary renal cell carcinoma is the second most common subtype, comprising 10-15% of renal cell carcinomas. Though the histologic features of this subtype were initially described in the 1990's, our understanding of the genetic and molecular characteristics of this disease have rapidly evolved over the past decade. In this review, we summarize the contemporary understanding of the clinical, morphologic, radiographic, and genetic characteristics of papillary renal cell carcinoma, as well as clinical considerations, current options for management, and prognosis.

Primary extrarenal papillary renal cell carcinoma presenting as a neck mass

Extrarenal primary renal cell carcinoma is an extremely rare entity with limited literature. Characteristic findings of renal cell carcinoma (RCC) at the metastatic site in the absence of a discrete radiological renal lesion can perplex both the clinician and pathologist. We report a case of metastatic primary extrarenal papillary RCC, who presented as a neck mass clinically and radiologically a paraaortic mass with normal bilateral native kidneys. The final diagnosis was aided by histopathological features, further confirmed by targeted immunohistochemical markers.

Is hypervascular papillary renal cell carcinoma present?

PURPOSE

We aimed to investigate atypical papillary renal cell carcinoma (PRCC) presenting with early contrast enhancement and late washout and to investigate the correlation between the CT attenuation value of the corticomedullary phase (CMP) of contrast-enhanced CT in PRCCs and the endothelial cell counts of these tumors.

METHODS

Twenty-two patients with pathologically confirmed PRCC were enrolled in this study. PRCCs were categorized into 18 typical PRCCs and 4 atypical PRCCs. The CT attenuation value of the lesion in the CMP was measured in the maximal section of the tumor using the region of interest. Microvessel density (MVD) was evaluated as a histopathologic parameter using tissue specimens immunohistochemically stained with an anti-ERG antibody. The CT attenuation value and MVD were compared between atypical and typical PRCCs using the Mann-Whitney U test, where p < 0.05 was considered significant. The correlations between CT attenuation value and MVD were evaluated in all PRCCs using single linear regression analysis.

RESULTS

The mean CT attenuation value and the MVD were significantly higher in atypical than in typical PRCCs. Correlation analyses revealed a weak positive correlation between the CT attenuation value and MVD.

CONCLUSIONS

We confirmed several cases of atypical PRCC that present with early contrast enhancement, such as clear cell renal cell carcinoma. In addition, a positive correlation was found between the CT attenuation value in the CMP of PRCCs and the vascular endothelial cell count.

Clinical utility of FDG PET/CT for primary and recurrent papillary renal cell carcinoma

PURPOSE

Papillary renal cell carcinoma (RCC) is the second most common subtype of RCC, after clear cell RCC. This study aimed to investigate the usefulness of FDG PET/CT in primary and recurrent papillary RCC, and the role of staging FDG PET/CT in predicting survival.

METHODS

A total of 66 patients with histopathologically confirmed papillary RCC who underwent either staging or restaging FDG PET/CT scans (30 had staging scans only, 28 had restaging scans only, 8 had both) were retrospectively included in this study. The sensitivity and specificity of restaging FDG PET/CT for detecting recurrence were assessed by histopathology and/or clinical follow-up as standard reference.

RESULTS

Staging FDG PET/CT scans were performed in 38 patients, of which 31 (81.5%) showed FDG-positive primary renal lesions. The SUVmax of high-grade (WHO grade 3 and 4) papillary RCCs were significantly higher than that of low-grade (WHO grade 1 and 2) tumors (9.44 ± 6.18 vs 4.83 ± 3.19, P = 0.008). The SUVmax was not significantly different between type 1 and type 2 papillary RCCs (5.71 ± 2.88 vs. 6.99 ± 5.57, P = 0.563). Of the 38 patients, 12 developed disease progression during the follow-up period. Patients with primary tumor SUVmax> 5.85 were associated with significantly shorter progression-free survival (PFS) than those with tumor SUVmax≤5.85 (P = 0.005). Restaging FDG PET/CT scans were performed in 36 patients with suspected recurrent papillary RCCs. FDG PET/CT showed a sensitivity and specificity of 100 and 72.7% for detecting recurrent disease. Comparison of PET/CT scans with CT/MRI imaging was available in 23 patients. FDG PET/CT revealed additional findings in 11 patients, mainly including lymph node and bone metastases. FDG PET/CT findings led to change in management in 5.3% (2/38) of patients in the staging setting and 16.7 (6/36) of patients in the restaging setting.

CONCLUSIONS

FDG PET/CT had a sensitivity of 81.5% for detecting primary papillary RCC, and tumor SUVmax derived from staging FDG PET/CT was a predictor of PFS. In the restaging process of papillary RCC, FDG PET/CT was very effective for detecting recurrent disease.

Anti-tumor efficacy of human anti-c-met CAR-T cells against papillary renal cell carcinoma in an orthotopic model

Chimeric antigen receptor (CAR)‐T cell therapy has shown salient efficacy in cancer immunotherapy, particularly in the treatment of B cell malignancies. However, the efficacy of CAR‐T for solid tumors remains inadequate. In this study, we displayed that c‐met is an appropriate therapeutic target for papillary renal cell carcinoma (PRCC) using clinical samples, developed an anti‐human c‐met CAR‐T cells, and investigated the anti‐tumor efficacy of the CAR‐T cells using an orthotopic mouse model as pre‐clinical research. Administration of the anti‐c‐met CAR‐T cells induced marked infiltration of the CAR‐T cells into the tumor tissue and unambiguous suppression of tumor growth. Furthermore, in combination with axitinib, the anti‐tumor efficacy of the CAR‐T cells was synergistically augmented. Taken together, our current study demonstrated the potential for clinical application of anti‐c‐met CAR‐T cells in the treatment of patients with PRCC.

A Concise Review of the Multimodality Imaging Features of Renal Cell Carcinoma

The evaluation of renal cell carcinoma (RCC) is routinely performed using the multimodality imaging approach, including ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). Ultrasonography is the most frequently used imaging modality for the initial diagnosis of renal masses. The modality of choice for the characterization of the renal mass is multiphasic CT. Recent advances in CT technology have led to its widespread use as a powerful tool for preoperative planning, reducing the need for catheter angiography for the evaluation of vascular invasion. CT is also the standard imaging modality for staging and follow-up. MRI serves as a problem-solving tool in selected cases of undefined renal lesions. Newer MRI techniques, such as arterial spin labeling and diffusion-weighted imaging, have the potential to characterize renal lesions without contrast media, but these techniques warrant further investigation. PET may be a useful tool for evaluating patients with suspected metastatic disease, but it has modest sensitivity in the diagnosis and staging of RCC. The newer radiotracers may increase the accuracy of PET for RCC diagnosis and staging. In summary, the main imaging modality used for the characterization, staging, and surveillance of RCC is multiphasic CT. Other imaging modalities, such as MRI and PET, are used for selected indications.

Discrimination of papillary renal cell carcinoma from benign proteinaceous cyst based on iodine and water content on rapid kV-switching dual-energy CT

PURPOSE

We aimed to evaluate whether rapid kV-switching dual energy CT (rsDECT) can discriminate between papillary renal cell carcinoma (RCC) and benign proteinaceous cysts (BPCs) based on iodine and water content.

METHODS

Twenty-four patients with histopathologically proven papillary RCC and 38 patients with 41 BPCs were retrospectively included. Patients with BPCs were eligible for inclusion when the cysts were stable in size and appearance for at least 2 years or proved to be a cyst on ultrasound or MRI. All patients underwent delayed phase (70-90 s) rsDECT. Iodine and water content of each lesion was measured on the workstation.

RESULTS

Of papillary RCC patients, 4 (16%) were female and 20 (84%) were male. Mean tumor size was 39±20 mm. Mean iodine and water content was 2.08±0.7 mg/mL and 1021±14 mg/mL, respectively. Of BPC patients, 9 were female and 29 were male. Mean cyst size was 20±7 mm. Mean iodine and water content was 0.82±0.4 mg/mL and 1012±14 mg/mL, respectively. There were significant differences between iodine and water contents of papillary RCCs and BPCs (P < 0.001). The best cutoff of iodine content for differentiating papillary RCC from BPC was 1.21 mg/mL (area under the curve [AUC]=0.97, P < 0.001, sensitivity 96%, specificity 88%, positive predictive value [PPV] 82%, negative predictive value [NPV] 97%, accuracy 91%,); the best cutoff of water content was 1015.5 mg/mL (AUC=0.68, P = 0.016, sensitivity 83%, specificity 56%, PPV 52%, NPV 85%, accuracy 66%).

CONCLUSION

An iodine content threshold of 1.21 mg/mL accurately differentiates papillary RCC from BPCs on a single postcontrast rsDECT. Despite having a high sensitivity, water content has inferior diagnostic accuracy.

Enhancement parameters of contrast-enhanced computed tomography for pancreatic ductal adenocarcinoma: Correlation with pathologic grading

BACKGROUND

Pancreatic ductal adenocarcinoma (PDA) is a malignancy with a high mortality rate and short survival time. The conventional computed tomography (CT) has been worldwide used as a modality for diagnosis of PDA, as CT enhancement pattern has been thought to be related to tumor angiogenesis and pathologic grade of PDA.

AIM

To evaluate the relationship between the pathologic grade of pancreatic ductal adenocarcinoma and the enhancement parameters of contrast-enhanced CT.

METHODS

In this retrospective study, 42 patients (Age, mean ± SD: 62.43 ± 11.42 years) with PDA who underwent surgery after preoperative CT were selected. Two radiologists evaluated the CT images and calculated the value of attenuation at the aorta in the arterial phase and the pancreatic phase (VA_arterial and VA_pancreatic) and of the tumor (VT_arterial and VT_pancreatic) by finding out four regions of interest. Ratio between the tumor and the aorta enhancement on the arterial phase and the pancreatic phase (TAR_arterial and TAR_pancreatic) was figured out through dividing VT_arterial by VA_arterial and VT_pancreatic by VA_pancreatic. Tumor-to-aortic enhancement fraction (TAF) was expressed as the ratio of the difference between attenuation of the tumor on arterial and parenchymal images to that between attenuation of the aorta on arterial and pancreatic images. The Kruskal-Wallis analysis of variance and Mann-Whitney U test for statistical analysis were used.

RESULTS

Forty-two PDAs (23 men and 19 women) were divided into three groups: Well-differentiated (n = 13), moderately differentiated (n = 21), and poorly differentiated (n = 8). TAF differed significantly between the three groups (P = 0.034) but TAR_arterial (P = 0.164) and TAR_pancreatic (P = 0.339) did not. The median value of TAF for poorly differentiated PDAs (0.1011; 95%CI: 0.01100-0.1796) was significantly higher than that for well-differentiated PDAs (0.1941; 95%CI: 0.1463-0.3194).

CONCLUSION

Calculation of TAF might be useful in predicting the pathologic grade of PDA.

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.

Hemosiderin deposition in papillary renal cell carcinoma and its potential to mask enhancement on MRI: analysis of 110 cases

OBJECTIVES

To evaluate the relationship between imperceptible T1 enhancement of papillary renal cell carcinoma (pRCC) on MR and intratumoral hemosiderin deposition.

METHODS

One hundred ten pRCCs (≤ 7 cm) were evaluated by MR with in- and opposed-phase spoiled gradient echo (GRE) and T1-weighted spoiled GRE with fat suppression before and after contrast. Hemosiderin deposition was assessed by SI_index and D_index on in- and opposed-phase images. SI_index and D_index are calculated as (SI_in - SI_opp)/(SI_in) × 100, where SI_in and SI_opp are tumor signal intensities on in- and opposed-phase images and (D_in)/(D_opp), where D_in and D_opp are tumor diameters on in- and opposed-phase images, respectively. The degree of tumor enhancement was classified as grade 1 (no), grade 2 (subtle), or grade 3 (definite). Tumor enhancement on CT was assessed when available.

RESULTS

Five (5%), 10 (9%), and 95 (86%) tumors were categorized as grades 1, 2, and 3 enhancement, respectively. The mean SI_index was - 33.9, - 25.3, and 1.00, whereas the mean D_index was 1.26, 1.05, and 1.00 in tumors with grades 1, 2, and 3 enhancement, respectively. Tumors with grade 1 enhancement had significantly lower SI_index (p = 0.001) and higher D_index (p = 0.005) than those with grade 3 enhancement. Among six tumors with grade 1 or 2 enhancement and available CT, four tumors showed > 20 HU enhancement.

CONCLUSIONS

pRCC with no subjective enhancement on contrast-enhanced MR showed hemosiderin deposition evident by lower SI_index and higher D_index. Hemosiderin deposition might mask the tumor enhancement on MR.

KEY POINTS

• 5% of papillary renal cell carcinoma showed imperceptible enhancement on contrast-enhanced MR. • Hemosiderin deposition in papillary renal cell carcinoma might mask the tumor enhancement on contrast-enhanced MR due to T2/T2*-shortening effects. • A renal lesion with extensive hemosiderin deposition but no perceptible enhancement on MR should be considered suspicious for papillary renal cell carcinoma.

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.

Diagnostic Accuracy of Multi-Parametric Magnetic Resonance Imaging for Tumor Staging of Bladder Cancer: Meta-Analysis

Purpose: Evaluate the diagnostic accuracy of multi-parametric magnetic resonance imaging (mp-MRI) for local staging of bladder cancer (BCa).

Materials and Methods: The databases of PubMed, Web of Science, Wanfang, and CNKI were searched for related literatures about BCa diagnosed by mp-MRI from January 1, 2000 to April 12, 2019. The strict inclusion and exclusion criteria were set up to extract records. The Quality Assessment of Diagnostic Accuracy Studies (QUADAS)-2 was used to evaluate quality of the candidate studies. The pooled sensitivity, specificity, positive likelihood ratio (+LR), negative likelihood ratio (−LR), and diagnostic odds ratio (DOR) were calculated to assess the diagnostic authenticity of mp-MRI. The summarized receiver operating characteristic (SROC) curve corresponding with the area under the curve (AUC) were analyzed to comprehensively evacuate the diagnostic value of mp-MRI.

Results: A total of 140 studies were retrieved by computer-based searching. After quality control, 4 studies with 259 patients were enrolled for meta-analysis. The pooled results showed 0.84 of sensitivity [95% confidence interval (CI) = 0.79-0.89], 0.91 of specificity (95% CI = 0.87–0.93), 8.24 of +LR (95% CI = 4.87–13.92), 0.18 of –LR (95% CI = 0.10–0.31), 49.42 of DOR (95% CI = 19.07–128.09), and 0.946 of AUC. The Spearman correlation analysis found no threshold effect (p = 0.684). A significant heterogeneity existed among 4 included studies with sensitivity (I² = 65.7%), specificity (I² = 60.0%) and diagnostic OR (I² = 67.5%). The Begg's test (p = 0.497) and the egger's test (p = 0.337) found no publication bias.

Conclusion: mp-MRI acts a good diagnostic performance for bladder cancer. It is plausible that mpMRIs can be used as an important method for bladder cancer staging.

Role of MR texture analysis in histological subtyping and grading of renal cell carcinoma: a preliminary study

PURPOSE

The study evaluated the usefulness of magnetic resonance imaging (MRI) texture parameters in differentiating clear cell renal carcinoma (CC-RCC) from non-clear cell carcinoma (NC-RCC) and in the histological grading of CC-RCC.

MATERIALS AND METHODS

After institutional ethical approval, this retrospective study analyzed 33 patients with 34 RCC masses (29 CC-RCC and five NC-RCC; 19 low-grade and 10 high-grade CC-RCC), who underwent MRI between January 2011 and December 2012 on a 1.5-T scanner (Avanto, Siemens, Erlangen, Germany). The MRI protocol included T2-weighted imaging (T2WI), diffusion-weighted imaging [DWI; at b 0, 500 and 1000 s/mm² with apparent diffusion coefficient (ADC) maps] and T1-weighted pre and postcontrast [corticomedullary (CM) and nephrographic (NG) phase] acquisition. MR texture analysis (MRTA) was performed using the TexRAD research software (Feedback Medical Ltd., Cambridge, UK) by a single reader who placed free-hand polygonal region of interest (ROI) on the slice showing the maximum viable tumor. Filtration histogram-based texture analysis was used to generate six first-order statistical parameters [mean intensity, standard deviation (SD), mean of positive pixels (MPP), entropy, skewness and kurtosis] at five spatial scaling factors (SSF) as well as on the unfiltered image. Mann-Whitney test was used to compare the texture parameters of CC-RCC versus NC-RCC, and high-grade versus low-grade CC-RCC. P value < 0.05 was considered significant. A 3-step feature selection was used to obtain the best texture metrics for each MRI sequence and included the receiver-operating characteristic (ROC) curve analysis and Pearson's correlation test.

RESULTS

The best performing texture parameters in differentiating CC-RCC from NC-RCC for each sequence included (area under the curve in parentheses): entropy at SSF 4 (0.807) on T2WI, SD at SSF 4 (0.814) on DWI b500, SD at SSF 6 (0.879) on DWI b1000, mean at SSF 0 (0.848) on ADC, skewness at SSF 2 (0.854) on T1WI and skewness at SSF 3 (0.908) on CM phase. In differentiating high from low-grade CC-RCC, the best parameters were: entropy at SSF 6 (0.823) on DWI b1000, mean at SSF 3 (0.889) on CM phase and MPP at SSF 5 (0.870) on NG phase.

CONCLUSION

Several MR texture parameters showed excellent diagnostic performance (AUC > 0.8) in differentiating CC-RCC from NC-RCC, and high-grade from low-grade CC-RCC. MRTA could serve as a useful non-invasive tool for this purpose.

Recurrent renal cell carcinoma leading to a misdiagnosis of polycystic liver disease: A case report

BACKGROUND

Polycystic liver disease (PCLD) with a large cystic volume deteriorates the quality of life of patients through substantial effects on the adjacent organs, recurrent cyst infections, cyst rupture, and hemorrhage. Surgical or radiological intervention is usually needed to alleviate these symptoms. We report a rare case of the cystic metastasis of renal cell carcinoma (RCC), which was misdiagnosed as PCLD, as a result of the clinical and radiological similarity between these disorders.

CASE SUMMARY

A 74-year-old female who had undergone nephrectomy for papillary-type RCC (PRCC) was suffering from abdominal pain and the recurrent intracystic hemorrhage of multiple cysts in the liver. Imaging studies and aspiration cytology of the cysts showed no evidence of malignancy. With a diagnosis of autosomal dominant polycystic liver disease, the patient received hepatectomy for the purpose of mass reduction and infectious cyst removal. Surgery was performed without complications, and the patient was discharged on postoperative day 14. Postoperatively, the pathology revealed a diagnosis of recurrent PRCC with cystic formation.

CONCLUSION

This case demonstrates the importance of excluding the cystic metastasis of a cancer when liver cysts are observed.

Uncommon malignant renal tumors and atypical presentation of common ones: a guide for radiologists

OBJECTIVE

While the typical imaging features of the more common RCC subtypes have previously been described, they can at times have unusual, but distinguishing features. Rarer renal tumors span a broad range of imaging features, but they may also have characteristic presentations. We review the key imaging features of atypical presentations of malignant renal tumors and uncommon malignant renal tumors.

CONCLUSION

Renal tumors have many different presentation patterns, but knowledge of the distinguishing MR and CT features can help identify both atypical presentation of common malignancies and uncommon renal tumors.

Renal epithelioid angiomyolipoma: magnetic resonance imaging characteristics

OBJECTIVE

The aim of the study was to analyze MR imaging features of renal epithelioid angiomyolipoma (EAML).

METHODS

This study included 17 patients with histopathologically confirmed renal EAML who underwent renal MRI scanning before radical or partial nephrectomy. MR images were retrospectively reviewed and correlated with pathological findings.

RESULT

Fifteen lesions (88.2%) appeared as round or oval. The tumor-kidney interface was round in 14 lesions (82.4%). Fifteen tumors (88.2%) presented mainly isointensity on T1WI, and eleven tumors (64.7%) presented mainly hypointensity on T2WI. Twelve lesions (70.6%) showed restricted diffusion on DWI, and the mean ADC value was 1.23 ± 0.28 × 10^-3mm²/s. Minimal fat component was identified as loss of signal intensity on opposed-phase MR images in 6 cases (35.3%). Sixteen lesions (100%) demonstrated inhomogeneous enhancement, and 7 of 16 masses (43.8%) showed reticular enhancement. Rapid wash-in and wash-out enhancement was seen in 13 masses (81.3%). In the corticomedullary phase, the mass showed markedly enhancement in 14 cases (87.5%). The irregular vessels and hemorrhage were detected in 4 cases (23.5%) and 7 cases (41.2%), respectively. One patient (5.9%) had a lymph node involvement at initial diagnosis, and showed distant metastasis after operation. In the immunohistochemical analysis, 15 tumors (88.2%) were positive for melanocytic marker (HMB45 or Melan-A), and all cases (100%) were negative for epithelial-associated markers (CK or AE1/AE3).

CONCLUSION

The presence of hypointensity on T2WI, restricted diffusion on DWI, round tumor-kidney interface, reticular, and marked enhancement (rapid wash-in and wash-out) should further raise suspicion for renal EAML. The diagnosis may be confirmed by pathological analysis.

Imaging following renal ablation: what can we learn from recurrent tumors?

PURPOSE

The purpose of the study was to evaluate the post-contrast appearance of local tumor progression (LTP) following renal ablation to better understand patterns of tumor recurrence and to optimize follow-up imaging protocols.

METHODS

From 2002 to 2015, 913 patients underwent 988 renal ablation procedures for treatment of 1064 tumors. LTP was identified in 24 (2.6%) patients during median imaging follow-up of 30 months (range 0-139). One patient with LTP was followed with non-contrast MRI only and was excluded from evaluation. Three body radiologists reviewed the contrast-enhanced CT and/or MRI follow-up imaging in the remaining 23 patients to determine the timing and imaging appearance of the recurrent tumor.

RESULTS

Local tumor progression was identified on contrast-enhanced CT or MRI at median 11 months (range 1 and 68) after renal ablation. Corticomedullary phase imaging was performed in 16/23 (70%) patients. LTP was identified on the corticomedullary phase in all cases, and was most conspicuous on the corticomedullary phase compared to any other phase of imaging in 15/16 (94%) patients. No cases of LTP were best visualized on non-contrast or excretory phase images.

CONCLUSIONS

Delayed recurrence following renal ablation is possible; therefore, extended follow-up is indicated in ablation patients. Almost all cases of LTP were best visualized on the corticomedullary phase of imaging, which should be included in any post-ablation imaging protocol. Excretory phase images were not required to diagnose LTP in any case and could be excluded from routine post-ablation follow-up.

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.

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.

Type 1 Papillary Renal Cell Carcinoma Presenting as an Infected Benign Renal Cyst: an Uncommon Presentation

We describe an unusual presentation of papillary renal cell carcinoma in a 40-year old male where radiological evaluation revealed a Bosniak type 2 cyst (probably benign), and clinical signs as well as symptoms also suggested an infected cyst l. However, on histopathological examination, an intra cystic type 1 papillary renal cell carcinoma was diagnosed. This is an extremely rare presentation of papillary renal cell carcinoma because it usually present as a heterogenous mass. Hence, even the radiologically benign cyst should be evaluated and managed cautiously.

Energy-Specific Optimization of Attenuation Thresholds for Low-Energy Virtual Monoenergetic Images in Renal Lesion Evaluation

OBJECTIVE

The purpose of this study was to determine in vitro and in vivo the optimal threshold for renal lesion vascularity at low-energy (40-60 keV) virtual monoenergetic imaging.

MATERIALS AND METHODS

A rod simulating unenhanced renal parenchymal attenuation (35 HU) was fitted with a syringe containing water. Three iodinated solutions (0.38, 0.57, and 0.76 mg I/mL) were inserted into another rod that simulated enhanced renal parenchyma (180 HU). Rods were inserted into cylindric phantoms of three different body sizes and scanned with single- and dual-energy MDCT. In addition, 102 patients (32 men, 70 women; mean age, 66.8 ± 12.9 [SD] years) with 112 renal lesions (67 nonvascular, 45 vascular) measuring 1.1-8.9 cm underwent single-energy unenhanced and contrast-enhanced dual-energy CT. Optimal threshold attenuation values that differentiated vascular from nonvascular lesions at 40-60 keV were determined.

RESULTS

Mean optimal threshold values were 30.2 ± 3.6 (standard error), 20.9 ± 1.3, and 16.1 ± 1.0 HU in the phantom, and 35.9 ± 3.6, 25.4 ± 1.8, and 17.8 ± 1.8 HU in the patients at 40, 50, and 60 keV. Sensitivity and specificity for the thresholds did not change significantly between low-energy and 70-keV virtual monoenergetic imaging (sensitivity, 87-98%; specificity, 90-91%). The AUC from 40 to 70 keV was 0.96 (95% CI, 0.93-0.99) to 0.98 (95% CI, 0.95-1.00).

CONCLUSION

Low-energy virtual monoenergetic imaging at energy-specific optimized attenuation thresholds can be used for reliable characterization of renal lesions.

Differentiation of renal cell carcinoma subtypes with different iodine quantification methods using single-phase contrast-enhanced dual-energy CT: areal vs. volumetric analyses

PURPOSE

To investigate the possibility of iodine quantification during a single nephrographic phase in characterizing renal cell carcinoma (RCC) subtypes and if there is a difference between areal and volumetric iodine quantification methods.

MATERIALS AND METHODS

This retrospective study included 110 patients with 113 histopathologically confirmed RCCs scanned by dual-energy CT at the nephrographic phase before surgeries. For each lesion, an areal measurement of the iodine concentration with maximum enhancement (I _{max enhan}) and the iodine concentration with maximum area among slices (I _{max area}), as well as a volumetric iodine concentration of the whole-tumor (I _volume), were evaluated by two independent radiologists. The diagnostic performances in a single nephrographic phase for characterizing RCC subtypes were evaluated, and three iodine quantification methods were compared with each other.

RESULTS

There were significant differences (clear cell vs. papillary and clear cell vs. chromophobe RCC) and no significant differences (papillary vs. chromophobe RCC) at the nephrographic phase in all three methods. The area under the receiver operating characteristic (ROC) curve (AUC) derived from the I _{max enhan} for discriminating clear cell from papillary RCC was significantly higher than that derived from the I _{max area} (P = 0.0357) and the I _volume (P = 0.0206), and no significant differences existed among the three methods in distinguishing clear cell RCC from chromophobe RCC. The reliability of all three parameters was very high with an interclass correlation coefficient (ICC) exceeding 0.8.

CONCLUSIONS

Iodine quantification in a single nephrographic phase can be used to differentiate RCC subtypes preoperatively, and the areal maximum enhancement iodine quantification would probably be the most appropriate approach.

Biomarker discovery for renal cancer stem cells

Characterised by high intra- and inter-tumor heterogeneity, metastatic renal cell carcinoma (RCC) is resistant to chemo- and radiotherapy. Therefore, the development of new prognostic and diagnostic markers for RCC patients is needed. Cancer stem cells (CSCs) are a small population of neoplastic cells within a tumor which present characteristics reminiscent of normal stem cells. CSCs are characterised by unlimited cell division, maintenance of the stem cell pool (self-renewal), and capability to give rise to all cell types within a tumor; and contribute to metastasis in vivo (tumourigenicity), treatment resistance and recurrence. So far, many studies have tried to establish unique biomarkers to identify CSC populations in RCC. At the same time, different approaches have been developed with the aim to isolate CSCs. Consequently, several markers were found to be specifically expressed in CSCs and cancer stem-like cells derived from RCC such as CD105, ALDH1, OCT4, CD133, and CXCR4. However, the contribution of genetic and epigenetic mechanisms, and tumor microenvironment, to cellular plasticity have made the discovery of unique biomarkers a very difficult task. In fact, contrasting results regarding the applicability of such markers to the isolation of renal CSCs have been reported in the literature. Therefore, a better understanding of the mechanism underlying CSC may help dissecting tumor heterogeneity and drug treatment efficiency.

Histologic subtype needs to be considered after partial nephrectomy in patients with pathologic T1a renal cell carcinoma: papillary vs. clear cell renal cell carcinoma

PURPOSE

We compared the oncological outcomes of papillary renal cell carcinoma (pRCC) with clear cell renal cell carcinoma (ccRCC) after partial nephrectomy (PN) in patients with pathologic T1a RCC.

METHODS

After excluding patients with synchronous multiple renal tumors, familial RCC, and pathologic stage T1b or above, 759 patients with ccRCC and 84 patients with pRCC were included. We assessed the impact of histologic subtypes on oncologic outcomes after PN in patients with pathologic T1a RCC (median follow-up duration, 67 months).

RESULTS

There was no difference in patient and tumor characteristics between the 2 groups, except Fuhrman grade (p = 0.006). Kaplan-Meier analysis identified 5-year recurrence-free survival of 98.7 and 95.6% in patients with ccRCC and pRCC, respectively. However, 10-year recurrence-free survival in patients with ccRCC and pRCC was 96.1 and 73.0%, respectively (p < 0.001). Recurrence ≥5 years post surgery was more common in patients with pRCC compared with those with ccRCC (0.3 vs. 4.8%; p < 0.001). In multivariate analysis, pRCC [hazard ratio (HR) 5.309; p = 0.001] was a significant risk factor for recurrence after PN in patients with pathologic T1a RCC, in addition to larger tumor size (HR 1.861; p = 0.038) and Fuhrman grade ≥3 (HR 5.176; p = 0.003).

CONCLUSIONS

In patients with pathologic T1a RCC, recurrence after PN occurred more commonly in pRCC compared with ccRCC. As over half of the recurrence cases in patients with pRCC occurred ≥5 years post surgery, a longer follow-up time is required, even for those with pathologic stage T1a disease.

Renal tumors with low signal intensities on T2-weighted MR image: radiologic-pathologic correlation

Accurate characterization of renal masses is essential for ensuring appropriate management. Low T2 signal intensity is a common feature of papillary renal cell carcinoma and fat-poor angiomyolipoma. Nonetheless, other types of renal cell carcinoma, oncocytoma, hemangioma, lymphoma, leiomyoma, and urothelial cell carcinoma also can show low signal intensities on T2-weighted imaging (T2WI). Histopathologic features that can lead to low T2 signal intensities in renal tumors include smooth muscle component, papillary architecture, a high nucleus-to-cytoplasm ratio, and hemorrhage. To establish an appropriate differential diagnosis for renal tumors on MRI, it is necessary to understand the relationship between the MR signal intensities and the histopathologic and morphologic features, in addition to contrast enhancement patterns and diffusion characteristics of the tumors.