Mesenchymal neoplasms of the kidney in adults: imaging spectrum with radiologic-pathologic correlation

Treatment of fat-poor renal angiomyolipoma with ectopic blood supply by fluorescent laparoscopy: A case report and review of literature

BACKGROUND

Renal angiomyolipoma and renal cell carcinoma are the most common benign and malignant tumors of the kidney respectively, and the preoperative differential diagnosis is crucial due to the wide difference in treatment methods. Fat-poor renal angiomyolipoma is a relatively rare type of in renal angiomyolipoma. Its fat imaging features are not obvious, and it is easily misdiagnosed as renal cell carcinoma.

CASE SUMMARY

We report the case of a 41-year-old man who complained of osphyalgia. Subsequent abdominal computed tomography scans revealed that a heterogeneous mass was seen in the lower pole of the right kidney, with the size of about 53 mm × 47 mm. And showed two right renal arteries, with the mass supplied by an ectopic vessel from the abdominal aorta. Fluorescent laparoscopic blockade of the right renal heterotopic artery and partial nephrectomy was performed. Based on histological and immunohistochemical findings, the tumor was diagnosed as fat-poor renal angiomyolipoma.

CONCLUSION

The use of fluorescent laparoscopy can effectively help intraoperative management, and the fluorescence pattern provided by intravenous indocyanine green can help suggest the final diagnosis, effectively guide the surgical decision-making, and avoid preoperative imaging diagnosis leading to nephrectomy for benign renal tumors, through fluorescent navigation of tumor supply vessel precise block, minimize the loss of renal function.

Utility of Ultrasound-Guided Attenuation Parameter (UGAP) in Renal Angiomyolipoma (AML): First Results

Angiomyolipoma (AML) are the most common benign solid renal mass. Differentiation from malignant tumours is essential. Imaging features in ultrasound may overlap between malignant lesions, especially between renal cell carcinoma (RCC) and AML. So far, sectional imaging has been necessary for reliable differentiation. The aim of this study is to evaluate the use of the ultrasound-guided attenuation parameter (UGAP), a recently established tool for assessing hepatic steatosis, in the differentiation of AMLs from other renal masses. Therefore, 27 patients with unknown solid renal masses were examined by ultrasound including UGAP. The attenuation was assessed qualitatively by attenuation map and quantitatively in comparison to the surrounding renal tissue. UGAP was applicable in 26/27 patients. Findings were compared with CT/MRI as the current imaging standard. A total of 18 AML and 9 other renal tumours were found. The diagnostic performance of B-Mode (hyperechogenic lesion) ultrasound was 77.8% in identifying AML. The diagnostic performance of the attenuation map showed a diagnostic performance of 92.6%, whereby UGAP measurements were successful in 76.9% of cases. Quantitatively, we found a significant difference (p < 0.034) in mean measured attenuation between AML (0.764 ± 0.162 dB/cm/MHz) vs. other renal tumours (0.658 ± 0.155 dB/cm/MHz). The best performance was found by a combined parameter of a hyperechogenic lesion with a positive attenuation map with an accuracy of 95.0%. In conclusion, UGAP may represent a possibility for differentiating solid renal lesions more accurately by ultrasound, especially classic hyperechoic AMLs from other renal lesions. Further studies are needed to increase the diagnostic reliability further.

Renal anastomosing hemangioma following partial nephrectomy for renal cell carcinoma: A case report

BACKGROUND

Renal anastomosing hemangioma (AH) is a rare benign vascular tumor characterized by unique histopathological features.

CASE SUMMARY

We report a highly unusual case of renal AH. A male patient had undergone partial nephrectomy for clear cell carcinoma of the kidney four years prior. A follow-up computed tomography scan in the third postoperative year revealed a new mass near the surgical site on the same side of the kidney, raising suspicions of tumor recurrence. However, the characteristics on contrast-enhanced magnetic resonance imaging and ultrasonography were more consistent with those of a benign lesion. The patient strongly insisted on undergoing surgery due to concerns about the possibility of renal cancer recurrence. Postoperative pathology confirmed the diagnosis of renal AH.

CONCLUSION

This case report presents the imaging features of a patient with rare renal AH and a history of renal clear cell carcinoma, providing broader insights into the differential diagnosis of new lesions after surgery for renal cell carcinoma.

Juxtaglomerular Cell Tumor Mimicking Renal Cell Carcinoma on 99m Tc-MIBI SPECT/CT

ABSTRACT

Juxtaglomerular cell tumor or reninoma is an extremely rare, typically benign, renin-secreting tumor of the kidney that causes secondary hypertension. We describe 99m Tc-MIBI SPECT/CT findings in a case of juxtaglomerular cell tumor. The renal tumor showed isodensity and photopenia on 99m Tc-MIBI SPECT/CT. This case indicates that juxtaglomerular cell tumor can appear cold on 99m Tc-MIBI SPECT/CT, mimicking renal cell carcinoma.

Epidemiology, treatment and outcomes of primary renal sarcomas in adult patients

To assess epidemiology, clinical presentation, treatment and overall survival of adult patients with renal sarcomas, the 2004-2016 SEER and NCDB databases were queried for adult patients diagnosed with renal sarcoma, calculating average annual age-adjusted incidence rates (AAIR) and average annual percentage change (AAPC) as well as overall survival (OS). In n = 1279 included renal sarcoma patients, AAIR remained constant over the study period (average 0.53 cases/1million; AAPC = 0.7, p = 0.6). Leiomyosarcoma (AAIR 0.14 cases/1 million) and malignant rhabdoid tumors (0.06 cases/1 million) were most common. Sarcoma histiotypes demonstrated considerable heterogeneity regarding demographic and cancer-related variables. Patients presented with advanced local extent (T3 33.3%; T4 14.2%) or distant metastases (29.1%) and commonly underwent surgical resection (81.6%). Longer OS was independently associated with younger age, female sex, lower comorbidity index, low T stage, negative surgical margins, absence of tumor necrosis or distant metastases and leiomyosarcoma histiotype (multivariable p < 0.05 each). Treatment efficacy varied according to sarcoma histiotype (interaction p < 0.001). Accounting for 0.25% of renal malignancies, renal sarcomas include 43 histiotypes with distinct epidemiology, clinical presentation, outcomes and sensitivity to systemic therapy, thereby reflecting soft-tissue sarcoma behavior. Renal sarcoma treatment patterns follow recommendations by renal cancer guidelines with surgical resection as the cornerstone of therapy.

Soft-Tissue Sarcomas of the Genitourinary Tract with Radiologic-Pathologic Correlation

Genitourinary tract soft-tissue sarcomas are rare neoplasms with varied pathologic and clinical features. While some of these tumors may be aggressive high-grade malignancies, others are low grade with a relatively better prognosis. Given that the grade and extent of the disease are important prognostic factors in these tumors, timely diagnosis is crucial. Unfortunately, most imaging features of these malignancies are not pathognomonic, and various histologic subtypes do not manifest with typical classic imaging features. Therefore, reliable differentiation of the various histologic tumor types is not always possible based solely on the radiologic manifestations. Imaging findings need to be considered in the context of clinical history in corroboration with radiologic-pathologic correlation. The authors discuss the specific imaging and pathologic characteristics of various genitourinary tract soft-tissue sarcomas, emphasizing diagnostic difficulties and differential diagnoses. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Differentiation between renal epithelioid angiomyolipoma and clear cell renal cell carcinoma using clear cell likelihood score

PURPOSE

Clear cell likelihood score (ccLS) may be a reliable diagnostic method for distinguishing renal epithelioid angiomyolipoma (EAML) and clear cell renal cell carcinoma (ccRCC). In this study, we aim to explore the value of ccLS in differentiating EAML from ccRCC.

METHODS

We performed a retrospective analysis in which 27 EAML patients and 60 ccRCC patients underwent preoperative magnetic resonance imaging (MRI) at our institution. Two radiologists trained in the ccLS algorithm scored independently and the consistency of their interpretation was evaluated. The difference of the ccLS score was compared between EAML and ccRCC in the whole study cohort and two subgroups [small renal masses (SRM; ≤ 4 cm) and large renal masses (LRM; > 4 cm)].

RESULTS

In total, 87 patients (59 men, 28 women; mean age, 55±11 years) with 90 renal masses (EAML: ccRCC = 1: 2) were identified. The interobserver agreement of two radiologists for the ccLS system to differentiate EAML from ccRCC was good (k = 0.71). The ccLS score in the EAML group and the ccRCC group ranged from 1 to 5 (73.3% in scores 1-2) and 2 to 5 (76.7% in scores 4-5), respectively, with statistically significant differences (P < 0.001). With the threshold value of 2, ccLS can distinguish EAML from ccRCC with the accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 87.8%, 95.0%, 73.3%, 87.7%, and 88.0%, respectively. The AUC (area under the curve) was 0.913. And the distribution of the ccLS score between the two diseases was not affected by tumor size (P = 0.780).

CONCLUSION

The ccLS can distinguish EAML from ccRCC with high accuracy and efficiency.

Potential clinical implications of an incidental renomedullary interstitial cell tumor in renal allograft biopsy

Renomedullary interstitial cell tumors (RMICTs) are often incidentally detected lesions at autopsy or resection of the kidney for other reasons. The RMICTs have not been reported in renal allograft biopsy. Overall, given the clinical implications of the differential diagnosis considered, such as morphologically similar neoplasms, interstitial fibrosis and tubular atrophy (IFTA), amyloidosis, and oxalosis, it is prudent to exclude these by an appropriate workup. Once excluded, the patients can be reassured. However, regular follow-up is recommended due to the propensity of RMICT to increase in size with age.

Wunderlich Syndrome: Comprehensive Review of Diagnosis and Management

Wunderlich syndrome (WS), which was named after Carl Wunderlich, is a rare clinical syndrome characterized by an acute onset of spontaneous renal hemorrhage into the subcapsular, perirenal, and/or pararenal spaces, without a history of antecedent trauma. Patients may present with a multitude of symptoms ranging from nonspecific flank or abdominal pain to serious manifestations such as hypovolemic shock. The classic symptom complex of flank pain, a flank mass, and hypovolemic shock referred to as the Lenk triad is seen in a small subset of patients. Renal neoplasms such as angiomyolipomas and clear cell renal cell carcinomas that display an increased proclivity for hemorrhage and rupture contribute to approximately 60%-65% of all cases of WS. A plethora of renal vascular diseases (aneurysms or pseudoaneurysms, arteriovenous malformations or fistulae, renal vein thrombosis, and vasculitis syndromes) account for 20%-30% of cases of WS. Rare causes of WS include renal infections, cystic diseases, calculi, kidney failure, and coagulation disorders. Cross-sectional imaging modalities, particularly multiphasic CT or MRI, are integral to the detection, localization, and characterization of the underlying causes and facilitate optimal management. However, large-volume hemorrhage at patient presentation may obscure underlying causes, particularly neoplasms. If the initial CT or MRI examination shows no contributary causes, a dedicated CT or MRI follow-up study may be warranted to establish the cause of WS. Renal arterial embolization is a useful, minimally invasive, therapeutic option in patients who present with acute or life-threatening hemorrhage and can help avoid emergency radical surgery. Accurate diagnosis of the underlying cause of WS is critical for optimal patient treatment in emergency and nonemergency clinical settings. ^©RSNA, 2023 Quiz questions for this article are available through the Online Learning Center.

Ultrasound Image-Based Deep Features and Radiomics for the Discrimination of Small Fat-Poor Angiomyolipoma and Small Renal Cell Carcinoma

We evaluated the performance of ultrasound image-based deep features and radiomics for differentiating small fat-poor angiomyolipoma (sfp-AML) from small renal cell carcinoma (SRCC). This retrospective study included 194 patients with pathologically proven small renal masses (diameter ≤4 cm; 67 in the sfp-AML group and 127 in the SRCC group). We obtained 206 and 364 images from the sfp-AML and SRCC groups with experienced radiologist identification, respectively. We extracted 4024 deep features from the autoencoder neural network and 1497 radiomics features from the Pyradiomics toolbox; the latter included first-order, shape, high-order, Laplacian of Gaussian and Wavelet features. All subjects were allocated to the training and testing sets with a ratio of 3:1 using stratified sampling. The least absolute shrinkage and selection operator (LASSO) regression model was applied to select the most diagnostic features. Support vector machine (SVM) was adopted as the discriminative classifier. An optimal feature subset including 45 deep and 7 radiomics features was screened by the LASSO model. The SVM classifier achieved good performance in discriminating between sfp-AMLs and SRCCs, with areas under the curve (AUCs) of 0.96 and 0.85 in the training and testing sets, respectively. The classifier built using deep and radiomics features can accurately differentiate sfp-AMLs from SRCCs on ultrasound imaging.

Angiomyolipoma of the kidney-Clinicopathological analysis of 52 cases

The renal angiomyolipoma (AML) is a benign tumor characteristically composed of fat, smooth muscle tissue, and vessels. We collected AMLs from our nephrectomy database, reclassified them according to their histological appearance, recorded the demographic, clinical, and pathological parameters, and compared them with oncocytoma (RO) and renal cell carcinoma (RCC). Immunohistochemistry was ordered in 41 cases. In 2224 nephrectomies, we found 52 AMLs with a 53 mm median size. The mean age was 52.76. Forty-eight tumors were sporadic, while four were hereditary. The revision resulted in 31 classic, 13 leiomyoma-like, five lipoma-like, two epithelioid, and one AML with epithelial cysts. SMA was diffusely positive, except for the epithelioid type, while MelanA harbored stronger expression than HMB45. AML was more frequent in females and appeared ten and 7 years earlier than RO and RCC, respectively. The follow-up time was 7.42 years, and neither tumor-related death nor relapse occurred. AML is rare in nephrectomies and develops primarily in females in their 50s with an average size of 50-60 mm at the surgery. The histological appearance in order of frequency is classic, leiomyoma-like, lipoma-like, epithelioid, and cystic. The MelanA, HMB45, and SMA immunohistochemistry can support the light-microscopic findings.

An Extremely Rare and Demanding Diagnosis of Primary Renal Synovial Sarcoma: A Case Report

Primary renal synovial sarcoma (PRSS) is an extremely rare malignancy. The diagnosis of PRSS is unforeseen due to the absence of clinical and radiological typical aspects. Here, we present a case of a 69-year-old male with complaints of hematuria and left lumbar pain. Abdominal-pelvic computed tomography scan with contrast injection showed a solid mass of 8cm diameter in the left kidney and renal vein tumor thrombus. The patient was further subjected to robotic-assisted left radical nephrectomy and renal vein thrombectomy. We concomitantly performed left adrenalectomy and paraaortic lymphadenectomy. Immunohistochemical and genetic analysis revealed PRSS. This entity is characterized by abnormal chromosomal translocation t(X;18)(p11.2; q11.2) and consequently the characteristic SYT-SSX fusion gene. Due to the disease's rarity and severity, diagnosis and management of PRSS rely upon a demanding and multidisciplinary approach.

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.

Primary Ewing’s sarcoma of the kidney: a rare masquerader of renal cell carcinoma on imaging

Background

The Ewing sarcoma family of tumors comprises a group of high-grade small round cell tumors, including Ewing sarcoma of bone, extra-skeletal Ewing sarcoma, peripheral primitive neuro-ectodermal tumor (PNET), and Askin tumor (thoraco-pulmonary PNET). They are more prevalent in young children and adolescents. Ewing's Sarcoma is an aggressive tumor majorly described in bones. Primary renal Ewing's sarcoma is an extremely rare entity, characterized by a very aggressive course, with very few reported cases in the literature.

Case presentation

We present an 18-year-old girl who presented with sudden onset left flank pain and hematuria. The patient had histopathology-proven primary renal Ewing's sarcoma, which was initially misdiagnosed as renal cell carcinoma on imaging.

Conclusions

Owing to its non-specific radiological appearance, a high index of suspicion and a systematic approach is essential for detection of renal Ewing’s Sarcoma.

Renal Parenchymal Leiomyoma Mimicking Renal Cell Carcinoma: A Case Report

BACKGROUND

Renal leiomyoma is a challenging diagnostic and therapeutic condition. Given that 90% of leiomyomas originate from the renal capsule, leiomyoma presenting as a renal parenchymal mass is extraordinarily rare.

CASE PRESENTATION

Herein, we report the clinical and imaging features of a patient with renal leiomyoma occurring in the renal parenchyma and mimicking renal cell carcinoma. We also review the clinical, imaging, and histological features of renal leiomyoma.

CONCLUSION

An initial partial, simple or radical nephrectomy according to tumor size and patient's underlying condition is suitable for larger, heterogeneous, and non-peripherally located tumors, even if they demonstrate hypointensity on T1- and T2-weighted images, considering the possibility of other diagnoses.

Renomedullary Interstitial Cell Tumor Mimicking Renal Cell Carcinoma: A Case Report

Renomedullary interstitial cell tumors are often incidentally identified either upon autopsy or kidney resection for other reasons. However, rare renomedullary interstitial cell tumor cases resulting in a clinical symptomatic mass have been reported. We present a case of renomedullary interstitial cell tumor that was manifested as an incidentally detected renal mass and mimicked renal cell carcinoma on the imaging features.

Hyperechoic Renal Masses: Differentiation of Angiomyolipomas from Renal Cell Carcinomas using Tumor Size and Ultrasound Radiomics

A retrospective single-center study was performed to assess the performance of ultrasound image-based texture analysis in differentiating angiomyolipoma (AML) from renal cell carcinoma (RCC) on incidental hyperechoic renal lesions. Ultrasound reports of patients from 2012 to 2017 were queried, and those with a hyperechoic renal mass <5 cm in diameter with further imaging characterization and/or pathological correlation were included. Quantitative texture analysis was performed using a model including 18 texture features. Univariate logistic regression was used to identify texture variables differing significantly between AML and RCC, and the performance of the model was measured using the area under the receiver operating characteristic (ROC) curve. One hundred thirty hyperechoic renal masses in 127 patients characterized as RCCs (25 [19%]) and AMLs (105 [81%]) were included. Size (odds ratio [OR] = 0.12, 95% confidence interval [CI]: 0.04-0.43, p < 0.001) and 4 of 18 texture features, including entropy (OR = 0.09, 95% CI: 0.01-0.81, p = 0.03), gray-level non-uniformity (OR = 0.12, 95% CI: 0.02-0.72, p = 0.02), long-run emphasis (OR = 0.49, 95% CI: 0.27-0.91, p = 0.02) and run-length non-uniformity (OR = 2.18, 95% CI: 1.14-4.16, p = 0.02) were able to differentiate AMLs from RCCs. The area under the ROC curve for the performance of the model, including texture features and size, was 0.945 (p < 0.001). Ultrasound image-based textural analysis enables differentiation of hyperechoic RCCs from AMLs with high accuracy, which improves further when combined with tumor size.

A case of atypical reninoma with mild hypertension and normal plasma renin activity but elevated plasma renin concentration

BACKGROUND

Reninoma is a rare, benign renal neoplasm. Typical clinical features include severe hypertension, secondary hyperaldosteronism, hypokalaemia and metabolic alkalosis caused by the overproduction of renin.

CASE PRESENTATION

A 25-year-old lean Chinese woman with no family history of hypertension was hospitalized for stage 1 hypertension that gradually developed over two years. Endocrine investigation showed hyperreninemia without hyperaldosteronism and hypokalaemia. Interestingly, although the patient had an elevated plasma renin concentration (PRC), her plasma renin activity (PRA) was in the normal range. Abdominal contrast-enhanced computed tomography (CT) scanning revealed a solid, low-density, renal cortical mass with delayed enhancement. Selective renal vein sampling (SRVS) was performed, and a lateralization of the renin secretion from the left kidney was found. Enucleation of the tumour led to a rapid remission of hypertension and hyperreninemia. Based on pathological findings, the patient was diagnosed with reninoma. Immunohistochemical staining of the tumour was positive for Renin, CD34, Vimentin, and synaptophysin (Syn) and negative for somatostatin receptor 2 (SSTR2) and chromogranin A (CgA).

CONCLUSIONS

Reninoma can present as mild hypertension without hyperaldosteronism and hypokalaemia. The clinical features of reninoma may depend on the degree of activation of the renin-angiotensin-aldosterone system (RAAS). PRC should be incorporated in the differential diagnosis of secondary hypertension.

An Ultrasonic-Based Radiomics Nomogram for Distinguishing Between Benign and Malignant Solid Renal Masses

Objectives

This study was conducted in order to develop and validate an ultrasonic-based radiomics nomogram for diagnosing solid renal masses.

Methods

Six hundred renal solid masses with benign renal lesions (n = 204) and malignant renal tumors (n = 396) were divided into a training set (n = 480) and a validation set (n = 120). Radiomics features were extracted from ultrasound (US) images preoperatively and then a radiomics score (RadScore) was calculated. By integrating the RadScore and independent clinical factors, a radiomics nomogram was constructed. The diagnostic performance of junior physician, senior physician, RadScore, and radiomics nomogram in identifying benign from malignant solid renal masses was evaluated based on the area under the receiver operating characteristic curve (ROC) in both the training and validation sets. The clinical usefulness of the nomogram was assessed using decision curve analysis (DCA).

Results

The radiomics signature model showed satisfactory discrimination in the training set [area under the ROC (AUC), 0.887; 95% confidence interval (CI), 0.860–0.915] and the validation set (AUC, 0.874; 95% CI, 0.816–0.932). The radiomics nomogram also demonstrated good calibration and discrimination in the training set (AUC, 0.911; 95% CI, 0.886–0.936) and the validation set (AUC, 0.861; 95% CI, 0.802–0.921). In addition, the radiomics nomogram model showed higher accuracy in discriminating benign and malignant renal masses compared with the evaluations by junior physician (DeLong p = 0.004), and the model also showed significantly higher specificity than the senior and junior physicians (0.93 vs. 0.57 vs. 0.46).

Conclusions

The ultrasonic-based radiomics nomogram shows favorable predictive efficacy in differentiating solid renal masses.

Olive Oil Improves While Trans Fatty Acids Further Aggravate the Hypomethylation of LINE-1 Retrotransposon DNA in an Environmental Carcinogen Model

DNA methylation is an epigenetic mechanism that is crucial for mammalian development and genomic stability. Aberrant DNA methylation changes have been detected not only in malignant tumor tissues; the decrease of global DNA methylation levels is also characteristic for aging. The consumption of extra virgin olive oil (EVOO) as part of a balanced diet shows preventive effects against age-related diseases and cancer. On the other hand, consuming trans fatty acids (TFA) increases the risk of cardiovascular diseases as well as cancer. The aim of the study was to investigate the LINE-1 retrotransposon (L1-RTP) DNA methylation pattern in liver, kidney, and spleen of mice as a marker of genetic instability. For that, mice were fed with EVOO or TFA and were pretreated with environmental carcinogen 7,12-dimethylbenz[a]anthracene (DMBA)-a harmful substance known to cause L1-RTP DNA hypomethylation. Our results show that DMBA and its combination with TFA caused significant L1-RTP DNA hypomethylation compared to the control group via inhibition of DNA methyltransferase (DNMT) enzymes. EVOO had the opposite effect by significantly decreasing DMBA and DMBA + TFA-induced hypomethylation, thereby counteracting their effects.

Renal AML Surgically Treated 33 Cases

BACKGROUND: Renal angiomyolipoma (RAML) is a rare benign neoplasm with a prevalence varying between 0.2% and 0.6% and a strong female predilection. They occur as sporadic, isolated entities in 80% of cases. The remaining 20% of angiomyolipomas (AMLs) develop in association with tuberous sclerosis complex or pulmonary lymphangioleiomyomatosis. AIM: We describe our 10-year experience with AML and discuss the treatment strategies employed at our center. METHODS: The medical records of all 33 patients with pathologically confirmed RAML treated either by nephrectomy or nephron-sparing surgery at our center over 10 years were reviewed for patient age and sex, tumor location and size, association with TBS. RESULTS: There were 28 females (84.8%) and 5 males (15.2%) with a median age that was 52 (range 22–74) years at the time of surgery. Thirty patients (90.9%) had sporadic isolated AML, and 3 patients (9.1%) had AML with TBS. The tumor was in the right kidney in 15 (45.5%) patients, in the left kidney in 17 (51.5%) patients, and bilateral in only 1 patient (3%) who was diagnosed with TBS. At presentation, flank pain was the main symptom in 23 patients (69.7%). CONCLUSIONS: Surgical resection of RAML provides short-term symptomatic relieve and long-term survival.

Primary renal sarcomas: imaging features and discrimination from non-sarcoma renal tumors

OBJECTIVES

To assess imaging features of primary renal sarcomas in order to better discriminate them from non-sarcoma renal tumors.

METHODS

Adult patients diagnosed with renal sarcomas from 1995 to 2018 were included from 11 European tertiary referral centers (Germany, Belgium, Turkey). Renal sarcomas were 1:4 compared to patients with non-sarcoma renal tumors. CT/MRI findings were assessed using 21 predefined imaging features. A random forest model was trained to predict "renal sarcoma vs. non-sarcoma renal tumors" based on demographics and imaging features.

RESULTS

n = 34 renal sarcomas were included and compared to n = 136 non-sarcoma renal tumors. Renal sarcomas manifested in younger patients (median 55 vs. 67 years, p < 0.01) and were more complex (high RENAL score complexity 79.4% vs. 25.7%, p < 0.01). Renal sarcomas were larger (median diameter 108 vs. 43 mm, p < 0.01) with irregular shape and ill-defined margins, and more frequently demonstrated invasion of the renal vein or inferior vena cava, tumor necrosis, direct invasion of adjacent organs, and contact to renal artery or vein, compared to non-sarcoma renal tumors (p < 0.05, each). The random forest algorithm yielded a median AUC = 93.8% to predict renal sarcoma histology, with sensitivity, specificity, and positive predictive value of 90.4%, 76.5%, and 93.9%, respectively. Tumor diameter and RENAL score were the most relevant imaging features for renal sarcoma identification.

CONCLUSION

Renal sarcomas are rare tumors commonly manifesting as large masses in young patients. A random forest model using demographics and imaging features shows good diagnostic accuracy for discrimination of renal sarcomas from non-sarcoma renal tumors, which might aid in clinical decision-making.

KEY POINTS

• Renal sarcomas commonly manifest in younger patients as large, complex renal masses. • Compared to non-sarcoma renal tumors, renal sarcomas more frequently demonstrated invasion of the renal vein or inferior vena cava, tumor necrosis, direct invasion of adjacent organs, and contact to renal artery or vein. • Using demographics and standardized imaging features, a random forest showed excellent diagnostic performance for discrimination of sarcoma vs. non-sarcoma renal tumors (AUC = 93.8%, sensitivity = 90.4%, specificity = 76.5%, and PPV = 93.9%).

Solid renal masses in adults

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

Radiologic and clinical results of transarterial ethanol embolization for renal angiomyolipoma

OBJECTIVE

We sought to determine the efficacy and safety of selective arterial embolization for renal angiomyolipoma (AML) using ethanol alone or ethanol with additional embolic materials and to analyze the factors influencing safety and efficacy.

METHODS

One hundred nineteen AMLs treated with embolization were included retrospectively during a 15-year period. Technical, radiologic, and clinical success were recorded and risk factor analysis was performed. Complications on follow-up images, post-embolization syndrome (PES), major complications, and changes in renal function were also evaluated.

RESULTS

Technical success was achieved in 106 of 119 tumors. Tumor size significantly decreased after treatment (reduction rate: 55%). Significant risk factors for tumor reduction included tumor enhancement on preprocedural CT and residual tumor staining. Radiologic success was achieved in 114 of 119 tumors (risk factor: residual tumor staining), and clinical success was achieved in 22 of 23 patients. Complications on follow-up images occurred in 40 of 119 tumors, and PES occurred in 53 of 104 patients. No major complications occurred. There were no cases of renal function impairment.

CONCLUSION

Selective transarterial embolization using ethanol alone or ethanol with additional embolic materials reduced AML size, alleviated symptoms, and can be performed safely without permanent impairment.

KEY POINTS

• Percutaneous transarterial ethanol embolization reduces AML size and alleviates symptoms. • Embolization can be performed safely without permanent impairment of renal function.

Inoperable Left Renal Vein Leiomyosarcoma Refractory to Chemotherapy Invades Inferior Vena Cava and Right Atrium: A Case Report

Mesenchymal stem cells differentiate into a plethora of cell types. These differentiated cell types include osteoblasts, chondrocytes, myocytes, and adipocytes. Sarcomas occur secondary to malignant transformation of these mesenchymal, pluripotent stem cells. Involuntary smooth muscle is responsible for the make up of hollow organs and vasculature in our body and is regulated by our autonomic nervous system, hormones, as well as chemical and local mediators. Cancer involving smooth muscle cells is designated as leiomyosarcoma (LMS). LMS can arise from any location in the body where smooth muscle is present and is frequently reported in the abdomen and pelvis, as well as the trunk, extremities, and throughout the retroperitoneum. 

A case of giant anastomosing hemangioma of the kidney with extramedullary hematopoiesis: A great mimicker

Anastomosing hemangioma (AH) are rare mesenchymal neoplasms affecting kidney with about 50 cases reported in English literature. In general, they are accidentally detected during examination or imaging done for nonspecific symptoms or wellness check-up. There are no key diagnostic features on the imaging modalities. The most common preoperative diagnosis has been a malignant primary renal carcinoma. Surgical resection remains the mainstay of treatment and of choice in symptomatic lesions. We are presenting a rare case of giant AH of the kidney mimicking a renal cell carcinoma on imaging. The lesions are characterized by anastomosing sinusoidal-like vascular spaces lined by banal endothelial cells with occasional hobnail morphology and associated with extramedullary hematopoiesis. The treatment of choice could be a conservative approach in small and asymptomatic lesions and patients with pre-existing renal dysfunction; hence, this entity should be in the differential of vascular renal neoplasms considering its proclivity to the urogenital tract. This is the first case in Indian literature to the best of our knowledge.

Xeroderma pigmentosum and renal leiomyosarcoma: A very rare case report association

INTRODUCTION

Xeroderma pigmentosum (XP) is a rare genetic disorder causing extreme sensitivity to ultraviolet (UV) rays. It is transmitted by an autosomal recessive mode. This disease is classically characterized by a high risk of skin cancer. The occurrence of extra-dermatological cancers in patients followed for XP has been rarely reported in the literature. We present the case of a 14-year-old adolescent with an exceptional association of XP and renal leiomyosarcoma.

PRESENTATION OF CASE

A 14-year-old adolescent was presented with an abdominal mass revealed by hematuria and abdominal pain. Computed tomography (CT) of the abdomen showed an enhancing, heterogeneous right renal mass, consistent with the features of renal tumor. After non conclusive biopsy, a total nephrectomy of the right kidney was performed. Based on gross specimen observation and immunochemical analysis, the patient was diagnosed with high-grade renal leiomyosarcoma. An adjuvant chemotherapy was indicated and the patient was referred to medical oncology. At 12 months follow-up, the patient is in total remission; The CT scan did not show any locoregional or distant recurrence CONCLUSION: The risk of renal tumor is increased in patients followed for XP. Attending physicians should ask for renal imaging at the slightest sign of clinical call.

Review of Value of CT Texture Analysis and Machine Learning in Differentiating Fat-Poor Renal Angiomyolipoma from Renal Cell Carcinoma

The diagnosis of patients with suspected angiomyolipoma relies on the detection of abundant macroscopic intralesional fat, which is always of no use to differentiate fat-poor angiomyolipoma (fp-AML) from renal cell carcinoma and diagnosis of fp-AML excessively depends on individual experience. Texture analysis was proven to be a potentially useful biomarker for distinguishing between benign and malignant tumors because of its capability of providing objective and quantitative assessment of lesions by analyzing features that are not visible to the human eye. This review aimed to summarize the literature on the use of texture analysis to diagnose patients with fat-poor angiomyolipoma vs those with renal cell carcinoma and to evaluate its current application, limitations, and future challenges in order to avoid unnecessary surgical resection.

Radiomics and Artificial Intelligence for Renal Mass Characterization

Radiomics allows for high throughput extraction of quantitative data from images. This is an area of active research as groups try to capture and quantify imaging parameters and convert these into descriptive phenotypes of organs or tumors. Texture analysis is one radiomics tool that extracts information about heterogeneity within a given region of interest. This is used with or without associated machine learning classifiers or a deep learning approach is applied to similar types of data. These tools have shown utility in characterizing renal masses, renal cell carcinoma, and assessing response to targeted therapeutic agents in metastatic renal cell carcinoma.

Contrast-Enhanced CT Texture Analysis for Distinguishing Fat-Poor Renal Angiomyolipoma From Chromophobe Renal Cell Carcinoma

Objective:

To evaluate the value of 2-dimensional (2D) and 3-dimensional (3D) computed tomography texture analysis (CTTA) models in distinguishing fat-poor angiomyolipoma (fpAML) from chromophobe renal cell carcinoma (chRCC).

Methods:

We retrospectively enrolled 32 fpAMLs and 24 chRCCs. Texture features were extracted from 2D and 3D regions of interest in triphasic CT images. The 2D and 3D CTTA models were constructed with the least absolute shrinkage and selection operator algorithm and texture scores were calculated. The diagnostic performance of the 2D and 3D CTTA models was evaluated with respect to calibration, discrimination, and clinical usefulness.

Results:

Of the 177 and 183 texture features extracted from 2D and 3D regions of interest, respectively, 5 2D features and 8 3D features were selected to build 2D and 3D CTTA models. The 2D CTTA model (area under the curve [AUC], 0.811; 95% confidence interval [CI], 0.695-0.927) and the 3D CTTA model (AUC, 0.915; 95% CI, 0.838-0.993) showed good discrimination and calibration (P > .05). There was no significant difference in AUC between the 2 models (P = .093). Decision curve analysis showed the 3D model outperformed the 2D model in terms of clinical usefulness.

Conclusions:

The CTTA models based on contrast-enhanced CT images had a high value in differentiating fpAML from chRCC.

Primary Renal Mesenchymal Neoplasms in Nephrectomy Specimens: A 16-Year Survey of Primary and Incidental Cases From a Single Institution

Context. Primary renal mesenchymal neoplasms are rare but diverse. Several neoplasms of mesenchymal derivation can arise as a primary renal mass; however, incidental tumors are identified in nephrectomies performed for end-stage renal disease or other malignant epithelial renal neoplasms. In this article, we document their frequencies with demographic information in nephrectomy specimens. Design. We retrospectively searched our database for nephrectomy specimens from the year 2000 to 2016. Results. A total of 224 cases were identified with an incidence rate of 4.4% (224/5128). One hundred ninety (85%) neoplasms were benign, 27 (12%) were malignant, and 7 (3%) were of intermediate biologic behavior. The majority of cases occurred in adults (93%, 208/224), and 39% of cases represented an incidental finding. The most common neoplasms were angiomyolipoma (58%) and renomedullary interstitial cell tumor (17%). Malignant mesenchymal kidney tumors are rare (0.39% of nephrectomy specimens). The most common adults' malignant tumors in our survey were synovial sarcoma and Ewing's sarcoma. Conclusion. Primary renal mesenchymal tumors are rare and are mostly benign in nature with many incidentally identified lesions. They arise in different age groups with malignant lesions usually presenting at a younger mean age.

Differentiation between fat-poor angiomyolipoma and clear cell renal cell carcinoma: qualitative and quantitative analysis using arterial spin labeling MR imaging

PURPOSE

To assess the diagnostic effectiveness of arterial spin labeling (ASL) MR imaging in differentiating fat-poor AML from clear cell renal cell carcinoma (ccRCC).

METHODS

In this prospective study, 29 ccRCC patients and 9 fat-poor AML patients underwent routine anatomical MRI and ASL at 3T before surgery after signing written informed consent form. For each tumor, tumor blood flow (TBF) was measured in a region of interest (ROI) which was positioned to outline the edge of the target lesions on ASL perfusion maps. Additionally, the mean TBF values were obtained by standardizing the TBF using a blood flow measurement in the reference ROI. Moreover, a cluster containing more than 10 voxels was chosen from the renal cortex and medulla area in normal contralateral kidney as a reference ROI to calculate tumor-to-cortex ratio and tumor-to-medulla ratio. Independent sample t test was used to examine the alteration among the groups of fat-poor AML and ccRCC. ASL images were together analyzed by two radiologists to assess the following characteristics of the renal mass: predominant SI in the tumor on ASL images was lower than, as same as, or higher than SI of the cortex. For qualitative variables, Fisher's exact test was employed to compare the proportions of these two groups. The sensitivity, specificity ,and accuracy required for discrimination of fat-poor AML from ccRCC were quantified using receiver operating characteristic (ROC) curve. The corresponding optimal cutoff value was obtained for each parameter as well.

RESULTS

The TBF value was significantly higher in ccRCC group than that in fat-poor AML (270.49 ± 78.88 ml/100 g/min vs. 146.68 ± 47.21 ml/100 g/min; P < 0.01). Both tumor-to-cortex and tumor-to-medulla ratios were notably higher in ccRCC group compared with those in fat-poor AML group (1.22 ± 0.26 vs. 0.74 ± 0.14, 3.13 ± 0.94 vs. 1.77 ± 0.55; P < 0.05). The values of area under the ROC curve (AUC) for TBF, tumor-to-cortex ratio, and tumor-to-medulla ratio were 0.931, 0.964, and 0.900, respectively. No significant difference in AUC values among these three measurements was observed. For qualitative variables, the SI of fat-poor AML was equal to or slightly lower than that of renal medulla and the SI of ccRCC was found to be higher than renal cortex in ASL.

CONCLUSION

ASL MRI performs well in differentiating fat-poor AML from ccRCC in both qualitative and quantitative analyses.

Whole-Tumor Quantitative Apparent Diffusion Coefficient Histogram and Texture Analysis to Differentiation of Minimal Fat Angiomyolipoma from Clear Cell Renal Cell Carcinoma

AIM

To evaluate the diagnostic value of whole-tumor quantitative apparent diffusion coefficient (ADC) histogram and texture analysis for differentiation of minimal fat angiomyolipoma (MFAML) from clear cell renal cell carcinoma (ccRCC).

MATERIALS AND METHODS

We retrospectively reviewed 27 patients with MFAML and 113 patients with ccRCC pathologically proven. All patients performed magnetic resonance imaging (MRI) including diffusion-weighted imaging (b = 0, 800s/mm²). Whole-tumor regions of interest were drawn on all slices of diffusion-weighted imaging to obtain histogram and texture parameters, including the mean ADC, median ADC, 10th, 25th, 75th, 90th percentiles ADC, standard deviation, skewness, kurtosis, and entropy. The Student's t test was used to compare the parameters between MFAML and ccRCC. Receiver operating characteristic curves analysis was used to compare the diagnostic value of each significant parameter.

RESULTS

MFAML had significantly lower mean ADC, median ADC, 10th, 25th, 75th, 90th percentiles ADC than ccRCC (p < 0.001, p < 0.001, p < 0.001, p < 0.001, p < 0.001, p < 0.001, respectively). Skewness of MFAML was significantly higher than that of ccRCC (p = 0.016). However, standard deviation, kurtosis, and entropy were not significantly different (p = 0.409, p = 0.085, p = 0.206, respectively). The 90th percentile ADC generated the highest AUC (AUC, 0.854; Sensitivity, 78.8%; Specificity, 81.5%) for differentiating MFAML from ccRCC.

CONCLUSION

Whole-tumor ADC histogram and texture analysis could be considered a useful and noninvasive method to help differentiate MFAML of ccRCC with higher accuracy.

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.

Magnetic resonance imaging (MRI) of the renal sinus

This article presents methods to improve MR imaging approach of disorders of the renal sinus which are relatively uncommon and can be technically challenging. Multi-planar Single-shot T2-weighted (T2W) Fast Spin-Echo sequences are recommended to optimally assess anatomic relations of disease. Multi-planar 3D-T1W Gradient Recalled Echo imaging before and after Gadolinium administration depicts the presence and type of enhancement and relation to arterial, venous, and collecting system structures. To improve urographic phase MRI, concentrated Gadolinium in the collecting systems should be diluted. Diffusion-Weighted Imaging (DWI) should be performed before Gadolinium administration to minimize T2* effects. Renal sinus cysts are common but can occasionally be confused for dilated collecting system or calyceal diverticula, with the latter communicating with the collecting system and filling on urographic phase imaging. Vascular lesions (e.g., aneurysm, fistulas) may mimic cystic (or solid) lesions on non-enhanced MRI but can be suspected by noting similar signal intensity to the blood pool and diagnosis can be confirmed with MR angiogram/venogram. Multilocular cystic nephroma commonly extends to the renal sinus, however, to date are indistinguishable from cystic renal cell carcinoma (RCC). Solid hilar tumors are most commonly RCC and urothelial cell carcinoma (UCC). Hilar RCC are heterogeneous, hypervascular with epicenter in the renal cortex compared to UCC which are centered in the collecting system, homogeneously hypovascular, and show profound restricted diffusion. Diagnosis of renal sinus invasion in RCC is critically important as it is the most common imaging cause of pre-operative under-staging of disease. Fat is a normal component of the renal sinus; however, amount of sinus fat correlates with cardiovascular disease and is also seen in lipomatosis. Fat-containing hilar lesions include lipomas, angiomyolipomas, and less commonly other tumors which engulf sinus fat. Mesenchymal hilar tumors are rare. MR imaging diagnosis is generally not possible, although anatomic relations should be described to guide diagnosis by percutaneous biopsy or surgery.

Urologic Diseases Germane to the Medical Renal Biopsy: Review of a Large Diagnostic Experience in the Context of the Renal Architecture and Its Environs

The kidney is one of the most complicated organs in development and is susceptible to more types of diseases than other organs. The disease spectrum includes developmental and cystic diseases, involvement by systemic diseases, iatrogenic complications, ascending infections and urinary tract obstruction, and neoplastic diseases. The diagnosis of kidney disease is unique involving 2 subspecialties, urologic pathology and renal pathology. Both renal and urologic pathologists employ the renal biopsy as a diagnostic modality. However, urologic pathologists commonly have a generous specimen in the form of a nephrectomy or partial nephrectomy while a renal pathologist requires ancillary modalities of immunofluorescence and electron microscopy. The 2 subspecialties differ in the disease spectrum they diagnose. This separation is not absolute as diseases of one subspecialty not infrequently appear in the diagnostic materials of the other. The presence of medical renal diseases in a nephrectomy specimen is well described and recommendations for reporting these findings have been formalized. However, urologic diseases appearing in a medical renal biopsy have received less attention. This review attempts to fill that gap by first reviewing the perirenal anatomy to illustrate why inadvertent biopsy of adjacent organs occurs and determine its incidence in renal biopsies followed by a discussion of gross anatomic features relevant to the microscopic domain of the medical renal biopsy. Unsuspected neoplasms and renal cysts and cystic kidney diseases will then be discussed as they create a diagnostic challenge for the renal pathologist who often has limited training and experience in these diseases.

Computed tomography and magnetic resonance imaging of peripelvic and periureteric pathologies

Peripelvic and periureteric areas are frequently overlooked in the imaging evaluations of the urinary system on computed tomography and magnetic resonance imaging. Several neoplastic and non-neoplastic disorders and diseases including lipomatosis, angiomyolipoma and angiolipomatous proliferation, vascular lesions, lymphangiomatosis, Rosai-Dorfman disease, Erdheim-Chester disease, extramedullary hematopoiesis, IgG4-related disease, lymphoma, mesenchymal tumors, trauma, and Antopol-Goldman lesion may involve these areas. Differentiation of these benign or malignant pathologies among themselves and from primary renal pathologies is of utmost importance to expedite the triage of patients for correct treatment approach. In this article, we aim to increase the awareness of the imaging specialists to the typical and atypical imaging features of the entities affecting these areas.

Thoracoabdominal imaging of tuberous sclerosis

Imaging of tuberous sclerosis complex has rapidly evolved over the last decade in association with increased understanding of the disease process and new treatment modalities. Tuberous sclerosis complex is best known for the neurological symptoms and the associated neuroimaging findings, and children with tuberous sclerosis complex require active surveillance of associated abnormalities in the chest, abdomen and pelvis. Common findings that require regular imaging surveillance are angiomyolipomas in the kidneys and lymphangioleiomyomatosis in the chest. However multiple rarer associations have been attributed to tuberous sclerosis complex and should be considered by radiologists reviewing any imaging in these children. In this review the authors discuss the spectrum of imaging findings in people with tuberous sclerosis complex, focusing on MR imaging findings in the chest, abdomen and pelvis.

Anastomosing hemangioma of the kidney: radiologic and pathologic distinctions of a kidney cancer mimic

Anastomosing hemangioma (ah) is a rare subtype of primary vascular tumour that can, clinically and radiologically, present similarly to malignant renal tumours such as renal cell carcinoma (rcc) and angiosarcoma. Rarely seen in the genitourinary system, the ah we report here occurred in a 40-year-old male patient diagnosed initially with rcc based on imaging and successfully treated by laparoscopic left radical nephrectomy, with adrenal sparing and perihilar lymph node dissection. The pathologic diagnosis of ah can be challenging on small biopsy specimens; we therefore opine that it is appropriate to excise these lesions to facilitate diagnosis and definitively exclude common renal cancers. However, in this review, we describe some radiologic and pathologic distinctions between ah and malignant tumours.

Imaging in retroperitoneal soft tissue sarcoma

Patients with retroperitoneal sarcoma can present to a variety of clinicians with non‐specific symptoms and retroperitoneal sarcomas can be incidental findings. Failure to recognize retroperitoneal sarcomas on imaging can lead to inappropriate management in non‐specialist centers. Therefore it is critical that the possibility of retroperitoneal sarcoma should be considered with prompt referral to a soft tissue sarcoma unit. This review guides clinicians through a diagnostic pathway, introduces concepts in response assessment and new imaging developments.

Anastomosing hemangioma simulating renal cell carcinoma

The anastomosing hemangioma is a recent described rare variant, which histologically simulates an angiosarcoma and occurs primarily in the genitourinary tract. We present a case of renal anastomosing hemangioma from a radiologic perspective, describing its imaging features and reviewing its presentation and management.

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.

Renal Angiomyolipoma: Radiologic Classification and Imaging Features According to the Amount of Fat

OBJECTIVE

The purposes of this article are to introduce the radiologic classifications of renal angiomyolipoma (AML) and the clinical implications, to show the imaging features of each type of AML, and to describe which types of AML should be biopsied.

CONCLUSION

Renal AML can be classified according to amount of fat as fat rich, fat poor, or fat invisible. To detect fat, one needs to thoroughly evaluate the entire AML by controlling the size and shape of the ROI. Fat-invisible AML should be biopsied, and fat-poor AML requires further investigation to determine whether biopsy is necessary to differentiate it from renal cell carcinoma. If differentiation between AML and renal cell carcinoma is not clear with CT and MRI, percutaneous biopsy may be performed.

Active Surveillance of Nonfatty Renal Masses in Patients With Lymphangioleiomyomatosis: Use of CT Features and Patterns of Growth to Differentiate Angiomyolipoma From Renal Cancer

OBJECTIVE

The objective of this study was to report our experience with active surveillance of nonfatty renal masses in a large cohort of patients with lymphangioleiomyomatosis (LAM), correlate their CT features and patterns of growth with histopathology results, and provide guidelines for management.

SUBJECTS AND METHODS

Yearly CT examinations were performed of 367 women (age range, 21-75 years; mean age, 47 years). For the 31 patients with 37 nonfatty renal masses that were biopsied, excised, or followed for ≥ 5 years, CT enhancement characteristics and patterns of growth were compared with the histopathology results.

RESULTS

Four of 37 nonfatty renal masses were biopsied without follow-up CT examinations: Two were heterogeneous renal cell carcinomas (RCCs), one was a heterogeneous nonfatty angiomyolipoma (AML), and one was homogeneous nonfatty AML. In the remaining 33 nonfatty renal masses with multiple follow-up CT examinations, two growth patterns were identified. Four showed a continuous increase in size of > 0.5 cm/y in some years, and all four in this first group were heterogeneous and were biopsy-proven RCC. The second group was composed of the remaining 29 masses. These 29 masses showed yearly no change, increase, or decrease in diameter. Eight were heterogeneous, and 21 were homogeneous. Of the masses showing a yearly increase, the increase was < 0.5 cm/y in all except one. In the one exception, the increase followed a decrease. Nine of the 29 masses were biopsied, and all nine were nonfatty renal masses (five homogeneous, four heterogeneous).

CONCLUSION

Our data provide further evidence in a large prospective study with longterm follow-up that active surveillance is an appropriate strategy in the management of nonfatty renal masses in patients with LAM. Our analysis of the growth patterns reveals duration of growth in addition to growth rate as criteria for biopsy or excision. Biopsy should be reserved for nonfatty renal masses that show sustained growth or growth > 0.5 cm/y during follow-up.

Do Incidental Hyperechoic Renal Lesions Measuring Up to 1 cm Warrant Further Imaging? Outcomes of 161 Lesions

OBJECTIVE

The purpose of this study was to determine the outcomes of hyperechoic renal lesions measuring 1 cm or less at ultrasound examination.

MATERIALS AND METHODS

This retrospective study included 161 hyperechoic renal lesions measuring 1 cm or less at ultrasound that were evaluated with follow-up ultrasound, CT, or MRI. Follow-up imaging examinations were reviewed to assess for definitive lesion characterization or size stability.

RESULTS

Follow-up included 11 unenhanced CT, 39 contrast-enhanced CT, 52 unenhanced and contrast-enhanced CT, two unenhanced MRI, 50 unenhanced and contrast-enhanced MRI, and 87 ultrasound examinations. At CT or MRI 58.4% of lesions were confirmed to be angiomyolipomas. At CT, one lesion represented a stone, and one a hyperdense cyst. At CT or MRI 11.8% of the lesions had no correlate; 3.1% were not visualized at follow-up ultrasound. An additional 23.6% were stable at 2-year follow-up imaging or beyond. Two lesions were evaluated with only contrast-enhanced CT less than 1 month after ultrasound, and the CT images did not show macroscopic fat or calcification or meet the criteria for a simple cyst. These lesions were considered indeterminate. One lesion in a 65-year-old man was imaged with unenhanced and contrast-enhanced CT 23 months after ultrasound, and the CT showed an increase in size, solid enhancement, and no macroscopic fat. This lesion was presumed to represent renal cell carcinoma. Overall, the one lesion presumed malignant and the two indeterminate lesions constituted 1.9% of the cohort. The other 98.1% of lesions were considered clinically insignificant.

CONCLUSION

Most hyperechoic renal lesions measuring 1 cm or smaller were clinically insignificant, suggesting that such lesions may not require additional imaging. Patient demographics, symptoms and risk factors for malignancy may help inform the decision to forgo follow-up imaging of such lesions.

Hamartomas from head to toe: an imaging overview

Hamartomas are tumours composed of mesenchymal tissues such as cartilage, fat, connective tissue and smooth muscle and can be found in virtually any organ system. These masses commonly develop sporadically, but are also seen in certain syndromes such as tuberous sclerosis or Carney triad. While their imaging appearance varies depending on the organ they arise from, findings are usually unique and a diagnosis can be confidently made. Radiologists must be aware of the clinical and imaging presentations of these lesions with the particular goal of avoiding unnecessary studies or invasive procedures. Furthermore, knowledge of common syndromic entities is crucial, as the radiologist may be the first to suggest the diagnosis.