Renal angiomyolipoma: a radiological classification and update on recent developments in diagnosis and management

Higher Risk Renal Angiomyolipomas: Surveillance Remains a Safe Management Option

INTRODUCTION

This retrospective study furthers our understanding of risk factors associated with hemorrhage and intervention in renal angiomyolipomas (R-AMLs), particularly in larger tumors (≥4 cm) and in childbearing-age (CBA; younger than 50 years) women. The objective was to refine risk stratification and optimize patient management.

METHODS

Review of our institutional database identified patients with radiographic R-AML from 1997 to 2023. Patient characteristics, R-AML characteristics, and clinical course were collected. Patients were grouped by management trajectories and analyzed across R-AML size, sex, and CBA woman status. Growth rates were modeled using linear mixed-effects regression.

RESULTS

Of the 162 patients in this cohort, 22% had large R-AMLs (≥4 cm), of which the majority (66%) were managed with surveillance and a substantial portion (43%) never underwent intervention. The 23% of the cohort who were CBA women were similarly primarily managed with surveillance (74%), and more than half never underwent intervention (53%). The median follow-up on surveillance was 5.4 years. There was a significantly higher modeled growth rate with larger baseline tumor size, but growth rate was not affected by CBA woman status. Most cases of bleeding were in patients with markedly enlarged R-AMLs with multiple risk factors, but there were no serious adverse events.

CONCLUSIONS

This study is enriched for large R-AMLs and uniquely focuses on CBA women. It reinforces the notion that most large R-AMLs are treated asymptomatically and do not necessarily represent the bleeding risk historically ascribed to them. It suggests that CBA woman status alone should not motivate R-AML treatment.

Renal angiomyolipomas: Typical and atypical features on computed tomography and magnetic resonance imaging

Angiomyolipomas (AMLs) represent the most common benign solid renal tumors. The frequency of their detection in the general population is increasing owing to advances in imaging technology. The objective of this review is to discuss computed tomography (CT) and magnetic resonance imaging findings for both typical and atypical renal AMLs, along with their associated complications. AMLs are typically defined as solid triphasic tumors composed of varying amounts of dysmorphic and tortuous blood vessels, smooth muscle components and adipose tissue. In an adult, a classical renal AML appears as a solid, heterogeneous renal cortical mass with macroscopic fat. However, up to 5% of AMLs contain minimal fat and cannot be reliably diagnosed by imaging. Fat-poor AMLs can appear as hyperattenuating masses on unenhanced CT and as hypointense masses on T2WI; other AMLs may be isodense or exhibit cystic components. Hemorrhage is the most common complication, and AMLs with hemorrhage can mimic other tumors, making their diagnosis challenging. Understanding the variable and heterogeneous nature of this neoplasm to correctly classify renal AMLs and to avoid misdiagnosis of other renal lesions is crucial.

Computed tomography and magnetic resonance imaging characteristics of renal cell carcinoma: Differences between subtypes and clinical evaluation

This review discusses the evaluation of renal cell carcinoma (RCC) subtypes using computed tomography (CT) and magnetic resonance imaging (MRI). RCC is a malignancy with different histopathological subtypes, constituting approximately 90% of adult kidney tumors. It has been reported that these subtypes show significant differences in terms of clinical behavior, treatment response, and prognosis. In the study, CT and MRI findings of subtypes such as clear cell RCC (ccRCC), papillary RCC (pRCC), chromophobe RCC (chRCC), medullary RCC (mRCC), collecting duct RCC (cdRCC), and multiloculated cystic RCC (mcRCC) were compared. It was stated that CT is the first-choice imaging method in the staging and surgical planning of RCC and provides detailed information about the tumor size, vascularity, and metastatic spread. On the other hand, it has been emphasized that MRI allows better characterization of RCC subtypes with its soft-tissue resolution and contrast agent usage advantage. The study draws attention to the different imaging features of each subtype and details the role of these findings in the clinical decision-making process. It has been stated that ccRCC exhibits intense contrast enhancement and rapid washout pattern in the corticomedullary phase on CT and appears hyperintense on T2A and hypointense on T1 weighted imaging (T1A) on MRI. It has been stated that pRCC has hypovascular features, has lower contrast enhancement, and has homogeneous borders. It has been stated that chRCC has a less vascular structure and exhibits moderate contrast enhancement in the corticomedullary phase. It has been reported that mRCC has invasive features and is usually diagnosed at an advanced stage while cdRCC has a very aggressive clinical course. It has been stated that mcRCC contains distinct cystic areas between the septa, has a well-circumscribed structure, and generally has a low malignancy potential. As a result, it has been stated that detailed evaluation of CT and MRI findings of RCC subtypes plays a critical role in the diagnosis, treatment, and prognosis of these subtypes. It has been emphasized that the findings presented in this study will contribute to the development of more targeted treatment approaches in RCC management.

Urologic Imaging of the Kidneys: Cancers and Mimics

Renal cell carcinoma (RCC) is a growing problem in global oncology, with a steadily increasing incidence, especially in developed regions. Its different histologic subtypes present different challenges in diagnosis and management. Advanced imaging techniques have a crucial role in distinguishing between these subtypes by highlighting unique radiographic features such as exophytic growth patterns, cystic components, and enhancement patterns. Practical suggestions discussed in this review include using chemical shift MRI to differentiate fat-poor angiomyolipomas from RCC, recognizing specific imaging markers such as pseudo-capsule in papillary RCC, and understanding the implications of negative pixel count in computed tomography scans.

Value of Contrast-Enhanced Ultrasound in the Diagnosis of Clear Cell Renal Cell Carcinoma: A Meta-Analysis

This meta-analysis aims to evaluate the accuracy of contrast-enhanced ultrasound (CEUS) in diagnosing clear cell renal cell carcinoma (ccRCC). Literature published in five databases was searched. Twelve studies were included. The pooled results showed sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio of CEUS were 79% (95% CI: 75%-83%), 84% (95% CI: 80%-88%), 4.97 (95% CI: 3.86-6.39), 0.24 (95% CI: 0.20-0.30), and 20.32 (95% CI: 13.84-29.84), respectively. The area under the summary receiver operating characteristic curve was 0.86. In conclusion, CEUS demonstrates high sensitivity and specificity in diagnosing ccRCC, showing good diagnostic accuracy.

Percutaneous radiofrequency ablation of an actively bleeding renal angiomyolipoma

We report a case of computed tomography-guided percutaneous radiofrequency ablation of a bleeding renal angiomyolipoma. Radiofrequency ablation was performed as an alternative to partial nephrectomy and super-selective renal artery embolization for ruptured renal angiomyolipoma with slow persistent bleeding in a patient with elevated serum creatinine levels and other comorbidities. Computed tomography-guided radiofrequency ablation successfully stopped the active hemorrhage and did not affect long-term renal function during the 3-year follow period. No complications were associated with the procedure. Radiofrequency ablation of a bleeding renal angiomyolipoma may be considered a more invasive surrogate procedure in an urgent setting; however, further studies are necessary to evaluate the long-term benefits of this approach and its overall impact on renal function compared to traditional methods.

Determinants of conventional and contrast-enhanced ultrasound diagnosis of fat-poor angiomyolipoma <5 cm

Purpose

This study aims to assess the diagnostic efficacy of conventional ultrasound (CUS) and contrast-enhanced ultrasound (CEUS) in detecting fat-poor angiomyolipomas(AML) with dimensions less than 5 cm. Additionally, the study seeks to identify independent indicators for predicting the presence of fat-poor AML.

Methods

We conducted a retrospective analysis of patients diagnosed with renal AML and renal cell carcinoma, who were admitted and underwent surgery at Fujian Provincial Hospital from January 2013 to October 2023. A total of 154 renal tumors were included (104 renal cell carcinomas and 50 fat-poor AMLs). Prior to radical or partial nephrectomy, these patients underwent both CUS and CEUS examinations. We systematically analyzed the features observed in CUS and CEUS, identified independent factors through multifactorial regression analysis, and evaluated diagnostic efficacy by calculating the area under the curve (AUC).

Results

Univariate analysis revealed significant distinctions in fat-poor AML concerning gender, age, morphology, internal hyperechoic features (starry-sky sign, crescent sign), enhancement uniformity, and delayed enhancement, all displaying significance compared to renal cell carcinoma (RCC) (p < 0.05). Multivariate analysis demonstrated that internal hyperechoic features (p < 0.01, Odds Ratio [OR] = 0.003, 95% Confidence Interval [CI]: 0.000-0.0028) and enhancement uniformity (p < 0.01, OR = 0.016, 95% CI: 0.001-0.229) independently predicted fat-poor AML. The Receiver Operating Characteristic (ROC) curve's area under the curve (AUC) for internal hyperechoic features (starry-sky sign, crescent sign) was 0.88 (95% CI: 0.80-0.95), with a sensitivity of 78.00%, specificity of 97.12%, positive predictive value of 92.85%, and negative predictive value of 90.18%. Conversely, the ROC curve AUC for enhancement uniformity was 0.70 (95% CI: 0.62-0.78), with a sensitivity of 96.00%, specificity of 44.23%, positive predictive value of 45.28%, and negative predictive value of 95.83%.

Conclusion

This study suggests that both CUS and CEUS possess discriminative value in differentiating fat-poor AMLs from RCCs. Notably, internal hyperechoic features (starry-sky sign, crescent sign) and uniform enhancement within renal tumors emerge as potential independent indicators for predicting fat-poor AML.

CT imaging analysis differentiating papillary renal neoplasm with reverse polarity from papillary renal cell carcinoma: combined with a radiomics model

PURPOSE

To assess the computed tomography (CT) findings of papillary renal neoplasm with reverse polarity (PRNRP) and develop a radiomics-based model to distinguish PRNRPs from papillary renal cell carcinomas (PRCCs).

MATERIALS AND METHODS

We analyzed 31 PRNRPs and 68 PRCCs using preoperative kidney CT. We evaluated CT features that could discriminate PRNRPs from PRCCs. A radiomics signature was constructed using features selected through a least absolute shrinkage and selection operator algorithm. A radiomics-based model incorporating a radiomics signature and subjective CT parameters using multivariate logistic regression was developed. The diagnostic performance of the CT parameters, radiomics model, and their combination was evaluated using the area under the curve (AUC).

RESULTS

Most of PRNRPs had a round shape (93.5%), well-defined margin (100%), and persistent enhancement (77.4%). Compared with PRCC, PRNRPs exhibited distinct CT features including small size (16.7 vs. 37.7 mm, P < 0.001), heterogeneity (64.5 vs. 32.4%, P = 0.004), enhancing dot sign (16.1 vs. 1.5%, P = 0.001), and high attenuation in pre-contrast CT (44.2 vs. 35.5 HU, P = 0.003). Multivariate analysis revealed smaller mass size (odds ratio [OR]: 0.9; 95% confidence interval [CI] 0.9-1.0, P = 0.013), heterogeneity (OR: 8.8; 95% CI 1.9-41.4, P = 0.006), and higher attenuation in pre-contrast CT (OR: 1.1; 95% CI 1.0-1.2, P = 0.011) as significant independent factors for identifying PRNRPs. The diagnostic performance of the combination model was excellent (AUC: 0.923).

CONCLUSION

Smaller tumor size, heterogeneity, and higher attenuation in pre-contrast CT were more closely associated with PRNRPs than with PRCCs. Though the retrospective design, small sample size, and single-center data of this study may affect the generalizability of the findings, combining subjective CT features with a radiomics model is beneficial for distinguishing PRNRPs from PRCCs.

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.

Qualitative and quantitative analysis of solid renal tumors by high-frame-rate contrast-enhanced ultrasound

OBJECTIVE

To analyze the characteristics of high-frame-rate contrast-enhanced ultrasound (H-CEUS) in solid renal tumors using qualitative and quantitative methods.

METHODS

Seventy-five patients who underwent preoperative conventional ultrasound (US), conventional contrast-enhanced ultrasound (C-CEUS), and H-CEUS examination of renal tumors were retrospectively analyzed, with a total of 89 renal masses. The masses were divided into the benign (30 masses) and malignant groups (59 masses) based on the results of enhanced computer tomography and pathology. The location, diameter, shape, border, calcification, and color doppler blood flow imaging (CDFI) of the lesions were observed by US, and the characteristics of the C-CEUS and H-CEUS images were qualitatively and quantitatively analyzed. The χ² test or Fisher's exact probability method was used to compare the US image characteristics between the benign and malignant groups, and the image characteristics of C-CEUS and H-CEUS between the benign and malignant groups. Moreover, the nonparametric Mann-Whitney test was used to compare the differences in C-CEUS and H-CEUS time-intensity curve (TIC) parameters.

RESULTS

Significant differences in gender, surgical approach, echogenicity, and CDFI were observed between the malignant and benign groups (p = 0.003, < 0.001, < 0.001, = 0003). Qualitative analysis also revealed significant differences in the mode of wash-out and fill-in direction between C-CEUS and H-CEUS in the malignant group (p = 0.041, 0.002). In addition, the homogeneity of enhancement showed significant differences between the two contrast models in the benign group (p = 0.009). Quantitative analysis indicated that the TIC parameters peak intensity (PI), deceleration time (DT) /2, area under the curve (AUC), and mean transition time (MTT) were significantly lower in the H-CEUS model compared to the C-CEUS model in both the benign and malignant groups. (all p < 0.001). In contrast, ascending slope of rise curve (AS) was significantly higher in the H-CEUS model compared to the C-CEUS model in the malignant group (p = 0.048).

CONCLUSIONS

In renal tumors, H-CEUS shows clearer internal enhancement of the mass and the changes in the wash-out period. The quantitative TIC parameters PI, DT/2, AUC, and MTT were lower in H-CEUS compared to C-CEUS. Both the quantitative and qualitative analyses indicated that H-CEUS better displays the characteristics of solid renal masses compared with C-CEUS.

Partial nephrectomy without prior arterial embolization in a case of giant renal angiomyolipoma

INTRODUCTION AND IMPORTANCE

This is a case of giant renal angiomyolipoma treated with partial nephrectomy without pre-embolization of the supplying arteries.

CASE PRESENTATION

The patient presented for regular checkup, a mass in the left flank was found on examination. No other symptoms were present. No history of medical or surgical importance was found.

CLINICAL DISCUSSION

CT scan revealed a heterogenous mass in the left kidney at the upper pole. The treatment options were discussed with the patient and he opted for complete removal of the mass. Partial nephrectomy was done without pre embolization of the arteries. The procedure went without complications, the blood loss was manageable during the operation (200 cc). The patient was admitted for 48 h post operation and was discharged shortly after. The excised mass was sent for histopathological examination, the report was received, the features of the mass was consistent with angiomyolipoma without other types of malignant masses present.

CONCLUSION

The takeaway is that partial nephrectomy provides a convenient option for treatment of giant renal angiomyolipomas. Preservation of the renal function, reduction of the recurrence risk or re embolization of the supplying arteries makes it a viable alternative for other treatment modalities.

Diagnostic value of imaging in patients with clear cell papillary renal cell carcinoma: A case series and literature review

Clear cell papillary renal cell carcinoma (CCPRCC) is a newly classified renal cell carcinoma with a low degree of malignancy. Its imaging features have not been studied deeply. Therefore, we reviewed the imaging features of CCPRCC. Solid CCPRCC shows high echo or isoecho mass on conventional ultrasound. Contrast enhanced ultrasound shows "fast forward and slow backward, uneven high enhancement". Computed tomography shows high enhancement and maximum enhancement in the cortical-medullary phase. Magnetic resonance imaging shows slightly low T1WI and high T2WI. This article aims to improve the understanding of CCPRCC by clinical radiologists and promote the accurate.

Renal epithelioid angiomyolipomas overexpress TFE3 and the TFE3-regulated gene TRIM63 in the absence of TFE3 rearrangement

Angiomyolipoma (AML) is a neoplasm within the perivascular epithelioid cell tumor family that occurs somewhat frequently in the kidney. Most are indolent and discovered incidentally, with rare tumors demonstrating malignant clinical behavior. A small subset of renal AMLs with epithelioid features are associated with aggressive behavior, and may demonstrate morphologic overlap with renal cell carcinomas (e.g., clear cell renal cell carcinoma (RCC), TFE3-rearranged RCC). Prior studies of spindle cell and epithelioid AMLs have identified rare examples with underlying TFE3 gene fusions. TFE3 protein expression (demonstrated by immunohistochemistry) with no evidence of concurrent TFE3 rearrangements has been reported previously in 4/24 AMLs (17%) (Argani et al. Am J Surg Pathol 34:1395-1406, 2010). Currently, the relationship between TFE3 protein expression, TFE3 fusions, and expression of TFE3-mediated genes remains incompletely understood in renal epithelioid AMLs. We sought to explore these relationships using TFE3 break-apart fluorescence in situ hybridization (FISH) and TRIM63 RNA in situ hybridization (ISH) on epithelioid AMLs with moderate to strong TFE3 expression by immunohistochemistry. RNA sequencing (fusion panel) was performed on two cases with negative FISH results to assess for FISH-cryptic gene fusions. The series comprised five epithelioid AMLs from four patients (three women, one man) aged 13 to 76 years. All were considered positive for TFE3 by immunohistochemistry (2 + /3 + expression). TRIM63 ISH was performed on four specimens from three patients, yielding positive results in 3/3 tumors (100%) that were successfully analyzed. TFE3 break-apart FISH was performed on all samples, demonstrating a TFE3 rearrangement in only 1/4 tumors (25%). RNA sequencing demonstrated the absence of productive TFE3 gene fusions in three tumors with negative break-apart TFE3 FISH results. This study demonstrates that renal epithelioid AMLs overexpress TFE3 and TFE3-mediated genes (TRIM63) even in the absence of TFE3 rearrangements. This finding could be explained by functional upregulation of TFE3 secondary to activation of the mammalian target of rapamycin complex 1 (mTORC1). Expression of TFE3 and TRIM63 in this tumor type represents a potential pitfall, given the morphologic and immunophenotypic overlap between epithelioid AML and TFE3-altered renal cell carcinoma.

Renal Angiomyolipoma with Tumor Thrombus in the Inferior Vena Cava and Right Atrium Accompanied by Renal Cell Carcinoma: A Case Report

Background: Renal angiomyolipoma (AML) without local invasion is generally considered benign. However, it may extend to the renal sinus, even the renal vein, or the inferior vena cava (IVC). In patients with non-tuberous sclerosis complex, coexistence of renal cell carcinoma (RCC) and renal AML is uncommon. Case presentation: A 72-year-old woman was incidentally found to have a solitary right renal mass with an IVC thrombus extending into the right atrium during a routine health checkup. Robot-assisted laparoscopic radical nephrectomy and thrombectomy were successfully performed through adequate preoperative examination and preparation. Two tumor lesions were found and pathologically confirmed as renal AML and RCC, and the tumor thrombus was derived from the renal AML. During the one-year follow-up period, no signs of recurrence or metastatic disease were observed. Conclusions: Renal AML with a tumor thrombus in the IVC and right atrium accompanied by RCC may occur, although rarely. In clinical practice, if preoperative manifestations differ from those of common diseases, rare diseases must be considered to avoid missed diagnoses. In addition, adequate examination and multidisciplinary discussions before making a diagnosis are necessary. For a level 4 tumor thrombus with no infringement of the venous wall, adoption of robot-assisted minimally invasive surgery, without extracorporeal circulation technology, is feasible.

Enhancing procedural decision making with cone beam CT in renal artery embolization

Cone-beam computed tomography (CBCT) has proven to be a safe and effective adjunctive imaging tool for interventional radiology. Nevertheless, limited studies have examined the application of CBCT in renal artery embolization (RAE). The objective of this study is to evaluate the role of CBCT in intra-procedural decision-making for RAE. This multicenter retrospective study included 40 consecutive patients (age: 55.9 ± 16.5 years; male, 55%) who underwent CBCT during RAE from January 2019 to January 2023. The additional information provided by CBCT was classified into Category 1 (no additional information), Category 2 (more information without changing the treatment plan), and Category 3 (valuable information that led to a change in the treatment plan). CBCT did not add unique information for four patients (10%) classified as Category 1. CBCT clarified ambiguous angiographic findings and confirmed the existing treatment plan for 19 patients (47.5%) graded as Category 2; complex vascular anatomy was explained (n = 13), and a correlation between vascular territory and target lesion was established (n = 6). CBCT offered valuable information that was not visible on digital subtraction angiography and changed the treatment plan for 17 patients categorized as Category 3; a mismatch between the vascular territory and the target lesion led to the identification of alternative (n = 3) and additional feeders (n = 8); and the extent of embolization was reduced by using automatic feeder detection software (n = 6). CBCT is an efficient tool that aids in the decision-making process during the embolization procedure by providing supplementary imaging information. This additional information enables the confident identification of target vessels, facilitates superselective embolization, prevents non-target embolization, and helps locate missing feeders.

Renal angiomyolipoma selective arterial embolization: Australian tertiary centre experience over 10 years

INTRODUCTION

The purpose of this study is to evaluate the patient selection methods, treatment outcomes, complications, clinical and radiological follow-up after renal angiomyolipoma (AML) treatment with selective arterial embolization (SAE) in an Australian metropolitan tertiary centre.

METHODS

This study presents a retrospective single-centre review of patients' medical records who underwent SAE for renal AML during the period of 1st January 2012 and 1st January 2023.

RESULTS

A total of 32 SAE procedures for renal AML occurred during the study period. Three episodes were classified as emergency cases [9.38%] and the remaining 29 were treated electively. Mean AML size pre-treatment was 69.45 mm (range = 33-177; SD = 31.69). All AMLs demonstrated hyper-vascularity on contrast-enhanced cross-sectional imaging (arterial-phase enhancement characteristics and/or prominent tortuous feeding vessels) [n = 32; 100%] or an intralesional aneurysm or pseudoaneurysm [n = 12; 42.85%]. Periprocedural complications [n = 3; 9.38%] included: one intralesional haemorrhage after embolization, one vascular access site complication, and one lipiduria-associated urinary tract infection. No patients suffered a life-threatening complication, non-target embolization, deterioration in renal function or death following SAE. Re-treatment with SAE was performed in only three patients [10.71%]. Hospital mean length of stay was 1.58 days. Median durations of clinical and radiological follow-up post-treatment were 493 days (range = 104-1645) and 501 days (range = 35-1774), respectively. Follow-up imaging revealed AML total size reduction in all cases [mean = -17.17 mm; -26.51%] and 50% had obliteration of lesion hyper-vascularity after one episode of SAE. Outpatient clinical follow-up signifies that none of the patients included in the study have re-presented with lesion haemorrhage after successful SAE.

CONCLUSION

In this study, renal AMLs were treated safely with a high degree of success by using SAE, and there were very low rates of periprocedural complications. Follow-up of patients after SAE treatment of renal AML should include both radiological (assessment for reduction in lesion vascularity and size) and clinical review in an outpatient clinic setting (either by an interventional radiologist or urologist).

Bilateral renal angiomyolipoma with venous invasion: A case report

Renal angiomyolipoma (AML) is a rare benign tumor of the kidney, often detected incidentally on radiological images as the presence of macroscopic fat characterizes them. In the majority of the cases, they are usually sporadic. Despite their benign nature, venous invasion, a rare occurrence in renal AMLs, poses management challenges. We present a case of bilateral renal AML in a 52-year-old female with a right renal vein and hepatic inferior vena cava invasion.

Stepwise algorithm using computed tomography and magnetic resonance imaging for differential diagnosis of fat-poor angiomyolipoma in small renal masses: A prospective validation study

OBJECTIVES

To validate the diagnostic accuracy of a stepwise algorithm to differentiate fat-poor angiomyolipoma (fp-AML) from renal cancer in small renal masses (SRMs).

METHODS

We prospectively enrolled 223 patients with solid renal masses <4 cm and no visible fat on unenhanced computed tomography (CT). Patients were assessed using an algorithm that utilized the dynamic CT and MRI findings in a stepwise manner. The diagnostic accuracy of the algorithm was evaluated in patients whose histology was confirmed through surgery or biopsy. The clinical course of the patients was further analyzed.

RESULTS

The algorithm classified 151 (68%)/42 (19%)/30 (13%) patients into low/intermediate/high AML probability groups, respectively. Pathological diagnosis was made for 183 patients, including 10 (5.5%) with fp-AML. Of these, 135 (74%)/36 (20%)/12 (6.6%) were classified into the low/intermediate/high AML probability groups, and each group included 1 (0.7%)/3 (8.3%)/6 (50%) fp-AMLs, respectively, leading to the area under the curve for predicting AML of 0.889. Surgery was commonly opted in the low and intermediate AML probability groups (84% and 64%, respectively) for initial management, while surveillance was selected in the high AML probability group (63%). During the 56-month follow-up, 36 (82%) of 44 patients initially surveyed, including 13 of 18 (72%), 6 of 7 (86%), and 17 of 19 (89%) in the low/intermediate/high AML probability groups, respectively, continued surveillance without any progression.

CONCLUSIONS

This study confirmed the high diagnostic accuracy for differentiating fp-AMLs. These findings may help in the management of patients with SRMs.

High-frame-rate contrast-enhanced ultrasound to differentiate between clear cell renal cell carcinoma and angiomyolipoma

BACKGROUND

To investigate the diagnostic efficacy of high-frame-rate contrast-enhanced ultrasound (H-CEUS) in differentiating between clear cell renal cell carcinoma (CCRCC) and angiomyolipoma (AML).

METHODS

A retrospective study was performed on the clinical data of 79 patients diagnosed with CCRCC and 31 patients diagnosed with AML at the First Affiliated Hospital of Nanchang University between October 2022 and December 2023. Conventional ultrasound (US) and H-CEUS examinations were conducted on all patients prior to surgery, dynamic images were recorded from the US, and the qualitative and quantitative parameters of H-CEUS were collected. The t-test, χ² test and non-parametric Mann-Whitney test were employed to assess differences in clinical data, US characteristics, and qualitative and quantitative parameters of H-CEUS between the CCRCC and AML groups. The independent risk factors of CCRCC were identified using binary logistic regression. The receiver operator characteristic (ROC) curve was constructed to evaluate the diagnostic effectiveness of clinical + US and H-CEUS in differentiating between CCRCC and AML.

RESULTS

The CCRCC group and the AML group exhibited significant differences in patient gender, operation mode, nodular echo, and nodule blood flow (χ²=11.698, -, -,=10.582; P<0.001, <0.001, <0.001, and = 0.014, respectively). In addition, the H-CEUS qualitative analysis demonstrated significant differences between the AML group and the CCRCC group with respect to enhancement mode, regression mode, peak intensity, enhancement uniformity, no enhancement, and presence or absence of pseudocapsule (χ²=41.614, -, -, = 2.758, = 42.099, -; P<0.001, <0.001, <0.001, 0.097, <0.001, and <0.001, respectively). The Arrival time (AT) in the CCRCC group was significantly shorter than that in the AML group, as determined by quantitative analysis of H-CEUS (Z=-3.266, P = 0.001). Furthermore, the Peak intensity (PI), Ascent slope (AS), and The area under the curve (AUC) exhibited significantly higher values in the CCRCC group compared to the AML group (Z=-2.043,=-2.545,=-3.565; P = 0.041, = 0.011, and <0.001, respectively). Logistic regression analysis indicated that only gender, nodule echo, the pseudocapsule, AS, and AUC of H-CEUS were independent risk factors of CCRCC. The ROC curve revealed that combining gender and nodule echo yielded a sensitivity of 92.4%, specificity of 64.5%, and an AUC of 0.847 in distinguishing between CCRCC and AML. When combining the H-CEUS parameters of pseudocapsule, AS, and AUC, the sensitivity, specificity, and AUC for distinguishing between CCRCC and AML were 84.8%, 96.8%, and 0.918, respectively. No statistically significant difference was observed in the diagnostic effectiveness of the two methods (Z=-1.286, P = 0.198). However, H-CEUS demonstrated better AUC and specificity.

CONCLUSIONS

H-CEUS enhances the sensitivity and specificity of differentiating between CCRCC and AML by improving the temporal resolution, offering a more precise diagnostic foundation for identifying the most appropriate therapy for patients.

Renal Collision Tumor: A Case of Small Cell Lung Cancer Metastasis to Renal Angiomyolipoma

ABSTRACT

A 68-year-old woman presented with chest pain and shortness of breath. Imaging revealed a left hilar mass biopsy-proven as small cell cancer. Concurrently, a macroscopic fat-containing renal lesion consistent with an angiomyolipoma was observed. Systemic therapy achieved stability in the lungs and bones, and palliative radiation targeted the left hilum. However, progressive lung disease and brain metastases necessitated stereotactic radiosurgery for brain lesions. Notably, the renal angiomyolipoma exhibited increased soft tissue component and new focal uptake on FDG PET/CT. Biopsy confirmed metastatic small cell lung cancer within the renal lesion. This case highlights a rare occurrence of a renal collision tumor involving small cell cancer and angiomyolipoma.

Natural History and Management of Ultrasound-detected Small Renal Angiomyolipoma

Background

Recent advances in imaging methods increased the incidental detection of small renal angiomyolipoma (AML). However, guidelines for managing small AML are lacking, and decisions about imaging frequency and timing of intervention are made on an individual basis. This study aims to investigate the clinical behavior of small sporadic AML and propose an optimal follow-up strategy.

Methods

The study is a retrospective analysis of 168 individuals who had hyperechoic lesions, suggestive of AML detected during abdominal ultrasound as a part of their health checkup. The clinical information of the individuals, including tumor characteristics and renal function, was reviewed. Statistical analysis was performed to identify factors associated with tumor growth and renal function.

Results

Most AMLs were small (≤20 mm) and did not exhibit malignant characteristics. The tumors showed a slow growth rate, with a mean growth rate of 0.24 mm/year. Only a small proportion of cases (1.2%) required intervention due to significant enlargement. Factors such as tumor size and gender were not significantly associated with tumor growth rate or renal function. However, younger patients showed a higher tumor growth rate and a more pronounced decline in renal function.

Conclusion

Small sporadic AMLs have a slow growth rate and little risk of malignancy. Neither tumor size nor gender was predictive factors for tumor growth or renal function. Nevertheless, close monitoring of tumor growth and renal function is advised, particularly in younger patients. This study highlights the need for further research and guidelines to establish an optimal surveillance protocol for small AMLs.

Autopsy findings of fatal retroperitoneal hemorrhage after traumatic rupture of bilateral renal angiomyolipoma

The present work reports the autopsy findings of a unique case characterized by fatal retroperitoneal hemorrhage following the traumatic rupture of bilateral renal angiomyolipomas. Renal angiomyolipomas are generally benign tumors with an unpredictable clinical course, ranging from asymptomatic to sudden rupture and hemorrhagic shock. They may be associated with genetic disorders such as tuberous sclerosis complex. The case under investigation is unprecedented in the medical literature due to its bilateral nature and fatal outcome. Autopsy analysis revealed an extensive retroperitoneal hemorrhage originating from bilateral ruptured tumors. Microscopic examination found features consistent with bilateral renal angiomyolipoma. Circumstantial information identified a traffic accident before the death, considering it as the cause of the tumors' traumatic rupture. In this case, due to the severity of the situation, immediate medical measures-such as fluid resuscitation, coagulopathy correction, and surgical treatment, which are usually lifesaving-could not be performed. This led to the patient being declared dead at the scene of the crash.

Multidisciplinary approach to the management of renal angiomyolipoma with inferior vena cava thrombus and pulmonary embolism: a case report

Renal angiomyolipoma (AML) is a benign tumor with rare venous extension. We present a case of a patient with renal AML with inferior vena cava (IVC) tumor thrombus and acute pulmonary embolism (PE). A 34-year-old female presented with chest pain. Imaging revealed a 5 cm right renal AML, with tumor thrombus into the renal vein and IVC, and acute left lower lobe PE. Right radical nephrectomy and caval thrombectomy were performed using intraoperative ultrasound. Rarely, these benign tumors generate thrombus with caval extension. The location of IVC thrombus guides surgical planning, which may involve suprahepatic IVC control or cardiopulmonary bypass. Early involvement of a multidisciplinary team with extensive preoperative planning can help achieve successful outcomes.

Endovascular treatment of sporadic renal angiomyolipoma presenting with Wunderlich syndrome

Angiomyolipomas are benign renal hamartomas with - fat, smooth muscle, and abnormal blood vessel (tortuous, dysmorphic) components. The risk of hemorrhage is related to size of the tumor, presence of aneurysm, associations with tuberous sclerosis. In this case report we review the case of a 42-year-old woman presenting with acute flank pain and decreased hemoglobin, who was diagnosed with AML with right renal artery pseudo aneurysm on CT. Subsequent coil embolization of feeding vessels and using PVA particles was successfully done. Selective embolization remains a minimally invasive, attractive option, and a nephron sparing approach.

Wunderlich Syndrome Managed with Angiomyolipoma Embolization - Renal Artery Anatomic Variant Augmenting Safe and Nephron-Sparing Intervention

Background

Wunderlich syndrome is an uncommon entity characterized by spontaneous, nontraumatic renal bleeding into the subcapsular and perirenal regions. The most frequent benign tumor, angiomyolipoma, is the most common cause of Wunderlich syndrome.

Case presentation

We report a case of Wunderlich syndrome in angiomyolipoma. Intratumoral pseudoaneurysm arising from feeders of an accessory renal artery supplying the lower pole of the kidney was selectively embolized. Rarely does a sporadic renal angiomyolipoma develop a giant pseudoaneurysm.

Conclusion

Transarterial embolization is imperative to control the bleeding or as a preventative measure to reduce the risk of intralesional pseudoaneurysm rupture. When vascular interventional facilities are unavailable, surgery may be necessary.

Hepatic Angiomyolipoma With Predominant Lipomatous Component: A Rare Entity

Hepatic angiomyolipoma (HAML) is a rare benign mesenchymal tumor with varying amounts of mature adipose tissue, smooth muscle cells, and thick-walled blood vessels. We present a rare case of hepatic angiomyolipoma (AML) with predominant lipomatous components. A 42-year-old female presented to the hospital with pain in the right lumbar region. On imaging, there was a large fat-predominant mass attached to the surface of the liver extending down to the lumbar region. On small biopsy, it was reported as a well-differentiated adipocytic neoplasm, and fluorescence in situ hybridization (FISH) studies performed for MDM2 were negative. On excision, histopathological examination showed predominantly fat components, but there were few epithelioid cells between adipocytes and thick-walled blood vessels. These cells were positive for Melan-A, HMB45, and smooth muscle actin (SMA) and negative for hepatocyte paraffin-1 (Hep Par1). Angiomyolipoma is a benign tumor and has a good prognosis with surgical excision. Few cases are associated with tuberous sclerosis.

Scientific Status Quo of Small Renal Lesions: Diagnostic Assessment and Radiomics

Background: Small renal masses (SRMs) are defined as contrast-enhanced renal lesions less than or equal to 4 cm in maximal diameter, which can be compatible with stage T1a renal cell carcinomas (RCCs). Currently, 50-61% of all renal tumors are found incidentally. Methods: The characteristics of the lesion influence the choice of the type of management, which include several methods SRM of management, including nephrectomy, partial nephrectomy, ablation, observation, and also stereotactic body radiotherapy. Typical imaging methods available for differentiating benign from malignant renal lesions include ultrasound (US), contrast-enhanced ultrasound (CEUS), computed tomography (CT), and magnetic resonance imaging (MRI). Results: Although ultrasound is the first imaging technique used to detect small renal lesions, it has several limitations. CT is the main and most widely used imaging technique for SRM characterization. The main advantages of MRI compared to CT are the better contrast resolution and tissue characterization, the use of functional imaging sequences, the possibility of performing the examination in patients allergic to iodine-containing contrast medium, and the absence of exposure to ionizing radiation. For a correct evaluation during imaging follow-up, it is necessary to use a reliable method for the assessment of renal lesions, represented by the Bosniak classification system. This classification was initially developed based on contrast-enhanced CT imaging findings, and the 2019 revision proposed the inclusion of MRI features; however, the latest classification has not yet received widespread validation. Conclusions: The use of radiomics in the evaluation of renal masses is an emerging and increasingly central field with several applications such as characterizing renal masses, distinguishing RCC subtypes, monitoring response to targeted therapeutic agents, and prognosis in a metastatic context.

The association between computed tomography attenuation value of renal angiomyolipoma associated with tuberous sclerosis complex and response to everolimus

BACKGROUND

The response to everolimus in patients with renal angiomyolipoma associated with tuberous sclerosis complex (TSC-RAML) varies among individuals. This study aims to identify potential factors associated with the response to everolimus.

METHOD

We retrospectively examined data encompassing age, gender, tumor size, computed tomography attenuation value (CT value), CT enhancement, and tumor reduction rate in patients with TSC-RAML undergoing everolimus in two previously registered clinical trials.

RESULT

A total of 33 participants (29.33 ± 6.63 years old, 20 females) were included. The correlation analysis conducted separately for tumors located in the left and right kidneys revealed significant negative correlations (P < 0.05) between tumor reduction rate and age, as well as tumor size. While significant positive correlations (P < 0.05) were observed between tumor reduction rate and unenhanced CT value as well as CT enhancement. Nonetheless, based on multiple linear regression analysis, unenhanced CT value emerged as the sole-independent predictor of tumor reduction rate among age, gender, tumor size, unenhanced CT value and CT enhancement for both left (coefficient = 0.00319, P < 0.0001) and right kidneys (coefficient = 0.00315, P = 0.0104). Notable reductions were observed in unenhanced CT value (- 3.81 vs - 24.70HU, P < 0.0001) and CT enhancement (48.16 vs 33.56HU, P < 0.0001) following a 3-month administration of everolimus. The decline in both unenhanced CT value and tumor size predominantly occurred within the initial 3 months, subsequently maintaining a relatively stable level throughout the treatment.

CONCLUSION

The unenhanced CT value of TSC-RAML showed an independent correlation with the response to everolimus, suggesting its potential as a predictor of everolimus efficacy in patients with TSC-RAML.

Renal angiomyolipoma: from imaging to intervention

A high volume of cross-sectional imaging has created a window of opportunity for radiologists to identify renal angiomyolipomas (AMLs). The purpose of this review is to help the reader recognise the spectrum of renal AML appearances using different imaging methods and to gain an understanding of the classic and atypical features for appropriate lesion characterisation. Risk factors for AML growth and rupture will be highlighted. An overview of the imaging features of acute AML rupture will be provided, principally relating to computed tomography (CT) assessment. A series of cases will be presented, including a case of peripartum renal AML rupture during Caesarean section leading to diagnostic dilemma. The indications for intervention and available treatment options will be considered: medical therapy, surgery, and interventional radiology (IR) techniques including their pros and cons. Emergency interventional radiology management with selective transarterial embolisation will be presented and analysed in relation to technique, angiographic appearances (pre and post embolisation) and associated complications.

Transcatheter arterial embolization followed by laparoscopic anatomic hepatectomy for spontaneous rupture of a giant hepatic angiomyolipoma: a case report

Hepatic angiomyolipoma is a rare and possibly cancerous mesenchymal tumor that consists of three components: blood vessels, smooth muscle cells, and adipose tissue. In this paper, we reported a case of a 36-year-old man who had a giant hepatic angiomyolipoma with spontaneous rupture and hemorrhage. The patient was admitted to our hospital with sudden upper abdominal pain for 3 h. A giant tumor was found in the left and caudate lobes of the liver, as well as significant blood collection around the liver and in the pelvis. Hemoglobin, liver function test results, and serum tumor maker levels were all within normal ranges. To prevent bleeding, emergency angiography and embolization were performed. During angiography, it was discovered that the tumor was supplied by the left hepatic artery and had a very rich internal blood supply. A massive left hepatic mass of about 11 cm in diameter was found bulging from the surface of the liver and rupturing there during laparoscopic exploration a week later. The rupture was strongly adhered to the smaller curvature of the stomach. The patient underwent laparoscopic left hemihepatectomy and caudate lobectomy, and the tumor specimen was brown, with clear boundaries with the surrounding normal liver parenchyma, and there were a large number of necrotic lesions inside the tumor. Histopathological results confirmed the mass as hepatic angiomyolipoma with negative resection margins. Immunohistochemical staining indicated that the tumor had positive homatropine methylbromide-45. After 13 months of follow-up, no tumor recurrence or metastasis occurred in the patient.

Development and external validation of the multichannel deep learning model based on unenhanced CT for differentiating fat-poor angiomyolipoma from renal cell carcinoma: a two-center retrospective study

PURPOSE

There are undetectable levels of fat in fat-poor angiomyolipoma. Thus, it is often misdiagnosed as renal cell carcinoma. We aimed to develop and evaluate a multichannel deep learning model for differentiating fat-poor angiomyolipoma (fp-AML) from renal cell carcinoma (RCC).

METHODS

This two-center retrospective study included 320 patients from the First Affiliated Hospital of Sun Yat-Sen University (FAHSYSU) and 132 patients from the Sun Yat-Sen University Cancer Center (SYSUCC). Data from patients at FAHSYSU were divided into a development dataset (n = 267) and a hold-out dataset (n = 53). The development dataset was used to obtain the optimal combination of CT modality and input channel. The hold-out dataset and SYSUCC dataset were used for independent internal and external validation, respectively.

RESULTS

In the development phase, models trained on unenhanced CT images performed significantly better than those trained on enhanced CT images based on the fivefold cross-validation. The best patient-level performance, with an average area under the receiver operating characteristic curve (AUC) of 0.951 ± 0.026 (mean ± SD), was achieved using the "unenhanced CT and 7-channel" model, which was finally selected as the optimal model. In the independent internal and external validation, AUCs of 0.966 (95% CI 0.919-1.000) and 0.898 (95% CI 0.824-0.972), respectively, were obtained using the optimal model. In addition, the performance of this model was better on large tumors (≥ 40 mm) in both internal and external validation.

CONCLUSION

The promising results suggest that our multichannel deep learning classifier based on unenhanced whole-tumor CT images is a highly useful tool for differentiating fp-AML from RCC.

Long-term efficacy of selective arterial embolisation of renal angiomyolipoma

OBJECTIVE

To evaluate the long-term efficacy of selective arterial embolisation in renal angiomyolipoma (AML), with emphasis on tumour shrinkage, potential regrowth and the necessity of supplementary procedures.  Material and methods: A retrospective review of all 58 consecutive embolisations at two institutions, between 1999 and 2018, was performed. Clinical notes, laboratory data and imaging were reviewed.

RESULTS

The overall complication rate was 6.8%, with no Clavien-Dindo grades III-V complications. Kidney function was unaffected by embolisation as measured by creatinine. Median radiological follow-up was 4.8 years (interquartile range [IQR]: 2.8-7.8), and median clinical follow-up was 7.5 years (IQR: 4.7-14.0). Decreasing AML size was observed in 96% of procedures. Maximal shrinkage (30% median diameter decrease; IQR: 15-44) was reached after median 2.2 years (IQR: 0.6-4.8). During follow-up, regrowth occurred in 38% of patients, and four bleeding episodes occurred in three patients with tuberous sclerosis. Growing size and/or rebleeding prompted a redo embolisation in 9% of spontaneous AML and 50% of tuberous sclerosis-associated AML.

CONCLUSIONS

Being a well-tolerated treatment with few complications, selective arterial embolisation renders a pronounced size-reduction in most patients with AML, and kidney function is preserved. Regrowth is common, and a radiological follow-up is necessary. Tuberous sclerosis is a risk factor for the need of reintervention.

Clinical Practice Guidelines for tuberous sclerosis complex-associated renal angiomyolipoma by the Japanese Urological Association: Summary of the update

New clinical issues have been raised through an interval of 7 years from the previous version (2016). In this study, we update the "Clinical Practice Guidelines for tuberous sclerosis complex-associated renal angiomyolipoma" as a 2023 version under guidance by the Japanese Urological Association. The present guidelines were cooperatively prepared by the Japanese Urological Association and Japanese Society of Tuberous Sclerosis Complex; committee members belonging to one of the two societies or specializing in the treatment of this disease were selected to prepare the guidelines in accordance with the "Guidance for preparing treatment guidelines" published by Minds (2020 version). The "Introduction" consisted of four sections, "Background Questions (BQ)" consisted of four sections, "Clinical Questions (CQ)" consisted of three sections, and "Future Questions (FQ)" consisted of three sections (total: 14 sections). Concerning CQ, an agreement was confirmed through voting by the committee members based on the direction and strength of recommendation, accuracy of evidence, and recommendation comments. The present guidelines were updated based on the current evidence. We hope that the guidelines will provide guiding principles for the treatment of tuberous sclerosis complex-associated renal angiomyolipoma to many urologists, becoming a foundation for subsequent updating.

Renal epithelioid angiomyolipoma: A case report

Epithelioid angiomyolipoma (EAML) of the kidney is an uncommon neoplasm with malignant potential. It can occur sporadically or be associated with tuberous sclerosis. EAML is a monotypic variant of angiomyolipoma (AML), which is classified as neoplasm of the perivascular epithelioid cell or perivascular epithelioid cell tumor. Due to its epithelioid nature and paucity of fat components, unlike classic AML, which has abundant adipose tissue with characteristic features on CT scans, it is difficult to distinguish EAML from renal cell carcinoma and fat-poor AML on CT or MRI preoperatively, which may lead to misdiagnosis and unnecessary nephrectomy. The present report describes two cases of renal EAML, which were successfully treated by laparoscopic surgery. Preoperative diagnosis had not been achieved until surgery was performed and histological analysis was accomplished. No local recurrence or distal metastasis was observed during follow-up. Although the differential diagnosis was challenging preoperatively, a diagnosis of EAML should be considered and surgical excision was the preferred treatment strategy for the patients with localized tumors.

Distinguishing lipid-poor angiomyolipoma from renal carcinoma using tumor shape

OBJECTIVES

To validate the "overflowing beer sign" (OBS) for distinguishing between lipid-poor angiomyolipoma (AML) and renal cell carcinoma, and to determine whether it improves the detection of lipid-poor AML when added to the angular interface sign, a previously-validated morphologic feature associated with AML.

METHODS

Retrospective nested case-control study of all 134 AMLs in an institutional renal mass database matched 1:2 with 268 malignant renal masses from the same database. Cross-sectional imaging from each mass was reviewed and the presence of each sign was identified. A random selection of 60 masses (30 AML and 30 benign) was used to measure interobserver agreement.

RESULTS

Both signs were strongly associated with AML in the total population (OBS: OR 17.4 95% CI 8.0-42.5, p < 0.001; angular interface: OR 12.6, 95% CI 5.9-29.7, p < 0.001) and the population of patients excluding those with visible macroscopic fat (OBS: OR 11.2, 95% CI 4.8-28.7, p < 0.001; angular interface: 8.5, 95% CI 3.7-21.1, p < 0.001). In the lipid-poor population, the specificity of both signs was excellent (OBS: 95.6%, 95% CI 91.9%-98%; angular interface: 95.1%, 95% CI 91.3%-97.6%). Sensitivity was low for both signs (OBS: 31.4%, 95% CI 24.0-45.4%; angular interface: 30.5%, 95% CI 20.8%-41.6%). Both signs showed high levels of inter-rater agreement (OBS 90.0% 95% CI 80.5 - 95.9; angular interface 88.6, 95% CI 78.7-94.9) Testing for AML using the presence of either sign in this population improved sensitivity (39.0%, 95% CI 28.4%-50.4%, p = 0.023) without significantly reducing specificity (94.2%, 95% CI 90%-97%, p = 0.2) relative to the angular interface sign alone.

CONCLUSIONS

Recognition of the OBS increases the sensitivity of detection of lipid-poor AML without significantly reducing specificity.

Radiological Features of T1a Renal Cell Carcinoma on Axial Unenhanced Computed Tomography

CT has become a commonly used diagnostic procedure in clinical practice, particularly in emergency healthcare delivery. Accordingly, the increase in CT usage has increased the likelihood of incidental detections (ID) of renal cell carcinomas (RCCs). This article discusses key points and limitations associated with the diagnosis and characterization of T1a RCC (≤4 cm in diameter) and shows how to improvise on the differentiation of T1a RCC with unenhanced CT (UE-CT). We retrospectively reviewed UE-CT findings of cases associated with the histopathologic diagnosis of T1a RCC and examined the discrimination capacity and radiological characteristics with regard to small RCCs (SRCCs). Detection and characterization of T1a RCC based on UE-CT are not easy in many cases due to limitations in CT findings, but there are notable radiological features to facilitate detection and differentiation. The growth pattern is important for the detection of SRCCs. Internal characteristic features (average attenuation, heterogeneity) are useful for the characterization of the RCC. In addition, CT image visualization techniques may help improve the detectability of RCCs on UE-CT. Radiological features are important in detecting SRCCs and facilitating further examination. In this study, we discuss some cases of T1a RCCs and evaluate the radiological characteristics of the tumors seen on UE-CT.

Shear wave elastography in the characterization of renal cell carcinoma and angiomyolipoma

BACKGROUND

Detection and characterization of renal lesions are common in daily clinical practice.

PURPOSE

To investigate the effectiveness of shear wave elastography (SWE), a novel radiological examination technique, in the characterization of renal masses.

MATERIAL AND METHODS

The study included a total of 68 patients (33 men, 35 women; mean age = 57.71 ± 12.08 years; age range = 19-83 years) who underwent SWE. SWE measurements were obtained at depths of 2-8 cm from the probe surface in two different positions from an analysis window of approximately 0.5 × 1.0 cm on ultrasound. The cutoff SWE was calculated for the differentiation of renal cell carcinoma (RCC) and angiomyolipoma (AML) by receiver operating characteristic (ROC) analysis. When the result was statistically significant, the sensitivity, specificity, accuracy, and positive and negative predictive values of the test were calculated.

RESULTS

Mass-to-parenchyma SWE ratios of RCCs were significantly higher than those of AMLs (P = 0.003). In ROC curve analysis, the SWE cutoff was 1.215 m/s to differentiate RCCs from AMLs. The area under the ROC curve was calculated as 0.74 (95% CI = 0.610-0.871, sensitivity = 70.7%, specificity = 70.6%, positive predictive value = 87.8%, negative predictive value = 44.4%).

CONCLUSION

The SWE technique is increasingly used and may be useful in distinguishing RCC and AML lesions, and especially clear cell and non-clear cell RCCs.

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.

Fat-poor renal angiomyolipoma with prominent cystic degeneration: A case report and review of the literature

BACKGROUND

Angiomyolipoma (AML), the most common benign tumor of the kidney, is usually composed of dysmorphic blood vessels, smooth muscle, and mature adipose tissue. To our knowledge, AML with cystic degeneration has rarely been documented. Cystic degeneration, hemorrhage, and a lack of fat bring great challenges to the diagnosis.

CASE SUMMARY

A 60-year-old man with hypertension presented with a 5-year history of cystic mass in his left kidney. He fell 2 mo ago. A preoperative computed tomography (CT) scan showed a mixed-density cystic lesion without macroscopic fat density, the size of which had increased compared with before, probably due to hemorrhage caused by a trauma. Radical nephrectomy was performed. Histopathological studies revealed that the lesion mainly consisted of tortuous, ectatic, and thick-walled blood vessels, mature adipose tissue, and smooth muscle-like spindle cells arranged around the abnormal blood vessels. The tumor cells exhibited positivity for human melanoma black-45, Melan-A, smooth muscle actin, calponin, S-100, and neuron-specific enolase, rather than estrogen receptor, progesterone receptor, CD68, and cytokeratin. The Ki-67 labeling index was less than 5%. The final diagnosis was a fat-poor renal AML (RAML) with prominent cystic degeneration.

CONCLUSION

When confronting a large renal cystic mass, RAML should be included in the differential diagnosis.

Sporadic Renal Angiomyolipoma: Can We Adopt a Uniform Management Protocol?

Renal angiomyolipomas (AMLs), formerly known as PEComas (tumors showing perivascular epithelioid cell differentiation) are common benign renal masses composed of a varying ratio of fat, blood vessels, and smooth muscles. They are largely asymptomatic and diagnosed incidentally on imaging.

The adipose tissue content is the factor that gives AMLs their characteristic appearance on imaging and makes them easily identifiable. However, the fat-poor or fat-invisible varieties, which are difficult to differentiate radiologically from renal cell carcinomas (RCCs), present a diagnostic challenge. It is thus essential to establish the diagnosis and identify the atypical and hereditary cases as they require more intense surveillance and management due to their potential for malignant transformation.

Multiple management options are available, ranging from conservative approach to embolization and to the more radical option of nephrectomy. While the indications for intervention are relatively clear and aimed at a rather small cohort, the protocol for follow-up of the remainder of the cohort forming the majority of cases is not well established. The surveillance and discharge policies therefore vary between institutions and even between individual practitioners. We have reviewed the literature to establish an optimum management pathway focusing on the typical AMLs.

Efficacy and safety of selective renal arterial embolization in renal angiomyolipoma: a prospective single-center study

Background

Preventing acute complication of renal angiomyolipoma (AML), preserving renal parenchyma, and improving long-term renal function are the treatment targets of renal angiomyolipoma. Treatment should be considered for symptomatic lesions or those who are at risk of complications, especially bleeding symptoms, which are linked to tumor size, angiogenic component grade, and presence of tuberous sclerosis complex (TSC). Selective arterial embolization (SAE) has become the new norm for preventive or emergency treatment of renal AMLs with minimally invasive selective targeting of small arterial feeders, we aimed to assess the efficacy and safety of selective renal arterial embolization (SAE) in the management of complicated renal angiomyolipoma and to detect the predictors of prophylactic SAE in cases of non-complicated AML.

Results

Bleeding symptoms were significantly more frequent in patients with TSC-associated renal AMLs (C = 0.333 and p = 0.036) and patients with intra-lesional aneurysm > 3 mm (C = 0.387 and p = 0.013). Overall success rate: thirty-three (91.7%) renal AMLs were successfully embolized with no recurrence. While three (8.3%) renal AMLs were not; one (2.8%) renal AML was not embolized due to technical failure and two (5.5%) renal AMLs showed recurrence. Primary (technical) success rate: thirty-three (86.9%) successful embolization, five (13.1%) arteriographies were done with failed embolization. The maximum diameter and volume of the lesions after SAE showed statistically significant reduction (z = 4.25 and p < 0.001).

Conclusions

SAE is an effective and safe technique to manage renal AMLs preoperatively or in an emergency. TSC-associated lesions, and intra-lesional aneurysms (aneurysms > 3 mm in diameter) were significantly more associated with bleeding symptoms, considering them significant predictors for prophylactic SAE in non-complicated AML.

Case report: A hybrid technique for a safe nephrectomy in a giant kidney angiomyolipoma

Background

Giant angiomyolipoma is usually associated with genetic syndromes and complications (spontaneous rupture and bleeding, hematuria, hypertension) and mass-related symptoms (flank and abdominal pain).

Case presentation

We present a case of a 20-year-old woman suffering from tuberous sclerosis who was referred to our hospital with a giant angiomyolipoma causing abdominal pain. A contrast-enhanced computed tomography showed a left angiomyolipoma, measuring 28 cm × 17 cm × 27 cm. After a multidisciplinary team discussion, the patient was submitted for a nephrectomy. Percutaneous temporary occlusion of the main renal artery was achieved through an endovascular balloon catheter. Through the balloon catheter guidewire, 2,500 IU of heparin was infused to reduce the risk of tumor vein thrombosis and venous embolism. This allowed a safe kidney manipulation through a left thoracoabdominal approach. The postoperative course was uneventful. Pathology showed a 40 cm × 30 cm × 9 cm and 10 kg AML. One year after surgery, the patient is on follow-up, and her estimated glomerular filtration is 120.5 ml/min/1.73 m².

Conclusion

The present case showed that the endovascular control of the main renal artery could be considered a useful approach to safely managing huge renal masses when renal hilar control is expected to be very difficult.

Cutaneous Angiomyolipoma-A Distinct Entity That Should Be Separated From Classic Angiomyolipoma: Complete Review of Existing Cases and Defining Fundamental Features

Cutaneous angiomyolipoma is a rare mesenchymal tumor that is demographically, clinically, and immunohistochemically distinct from its renal and extrarenal counterparts. We present a case of cutaneous angiomyolipoma in the right retroauricular area of a 35-year-old male patient and provide a broad systematic review of the literature and the largest compilation of cutaneous angiomyolipomas reported to date. According to the findings presented in this review, we conclude that cutaneous angiomyolipoma should be completely separated from renal and extrarenal angiomyolipomas and therefore be considered a distinct entity in the classification of skin tumors.

Renal Epithelioid Angiomyolipoma with Epithelial Cysts Mimicking Cystic Renal Cell Carcinoma: A Case Report of Combination of Two Rare Entities

Renal angiomyolipomas (AMLs) are typically solid tumors, but there have been few reports of a rare cystic variant of AML. AML with epithelial cysts, where the epithelial cyst has a cuboidal epithelial lining, account for the majority of them. Next, epithelioid AML (EAML) with cystic changes due to hemorrhage and necrosis, which is composed of epithelioid cells with abundant eosinophilic cytoplasm, have also been reported. These rare cystic types of AML can be mistaken for other cystic tumors, such as cystic renal cell carcinoma, in preoperative imaging. We report the imaging findings of a rare case of EAML with epithelial cysts.

Circulating exosomal mRNA signatures for the early diagnosis of clear cell renal cell carcinoma

BACKGROUND

There are no proven tumor biomarkers for the early diagnosis of clear cell renal cell carcinoma (ccRCC) thus far. This study aimed to identify novel biomarkers of ccRCC based on exosomal mRNA (emRNA) profiling and develop emRNA-based signatures for the early detection of ccRCC.

METHODS

Four hundred eighty-eight participants, including 226 localized ccRCCs, 73 patients with benign renal masses, and 189 healthy controls, were recruited. Circulating emRNA sequencing was performed in 12 ccRCCs and 22 healthy controls in the discovery phase. The candidate emRNAs were evaluated with 108 ccRCCs and 70 healthy controls in the test and training phases. The emRNA-based signatures were developed by logistic regression analysis and validated with additional cohorts of 106 ccRCCs, 97 healthy controls, and 73 benign individuals.

RESULTS

Five emRNAs, CUL9, KMT2D, PBRM1, PREX2, and SETD2, were identified as novel potential biomarkers of ccRCC. We further developed an early diagnostic signature that comprised KMT2D and PREX2 and a differential diagnostic signature that comprised CUL9, KMT2D, and PREX2 for RCC detection. The early diagnostic signature displayed high accuracy in distinguishing ccRCCs from healthy controls, with areas under the receiver operating characteristic curve (AUCs) of 0.836 and 0.830 in the training and validation cohorts, respectively. The differential diagnostic signature also showed great performance in distinguishing ccRCCs from benign renal masses (AUC = 0.816), including solid masses (AUC = 0.810) and cystic masses (AUC = 0.832).

CONCLUSIONS

We established and validated novel emRNA-based signatures for the early detection of ccRCC and differential diagnosis of uncertain renal masses. These signatures could be promising and noninvasive biomarkers for ccRCC detection and thus improve the prognosis of ccRCC patients.

Pitfalls in the diagnosis and treatment of fat-poor angiomyolipoma of the renal pelvis mimicking urothelial carcinoma: report of three rare cases

Angiomyolipoma (AML) represents the most frequent benign neoplasm of the kidney. It arises mostly in the cortex and protrudes into the perirenal space. It is extremely rare for a fat-poor AML to originate from the renal sinus, invade the pelvis, and present with hematuria. Because of the rarity of this lesion, differentiating it from a urothelial carcinoma is difficult, thereby making a preoperative diagnosis and management complex and challenging. We report three cases of fat-poor AML centered within the renal pelvis mimicking a urothelial carcinoma that underwent radical nephroureterectomy. The clinical characteristics, surgical management, and prognosis are discussed to achieve better preoperative evaluation of these entities. This is the first report of fat-poor AMLs involving the renal pelvis and presenting with hematuria. Nephron-sparing treatment is crucial for patients with these entities. Accurate diagnosis may allow partial resection or kidney-preserving treatment.

Spontaneous rupture of renal angiomyolipoma and its management: A case report

a) Introduction and Importance

Angiomyolipomas of kidney are benign lesions that are generally an incidental finding on imaging. Rupture of angiomyolipoma is rare and fatal complication that requires early intervention.

b) Case Presentation

A 38 year old male patient presented with symptoms of right flank pain for 2 days. On clinical examination patient looked anxious, pale with right flank tenderness, guarding and signs of shock.

c) Clinical findings and investigations

CT scan showed renal angiomyolipoma with aneurysm formation and bleed from the lesion. Blood profile revealed low hemoglobin.

d) Interventions and Outcome

Right nephrectomy performed along 6 cycles of cardiopulmonary reususcitaion done with stable post operatively vitals.

e) Conclusion

Early diagnosis of complication of angiomyolipoma requires thorough clinical examination and judicious use of imaging. Immediate embolization or surgery must be performed for better outcome and survival rate.

•

Angiomyolipoma is composed of fat, smooth muscle and blood vessels and presents among 0.3% of the population.

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Renal angiomyolipoma are prone to aneurysm formation and bleed, however a nontraumatic spontaneous renal hemorrhage from a sporadic renal angiomyolipoma is a rare condition.

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Mostly angiomyolipoma are asymptomatic and are diagnosed incidentally. CT scan is the diagnostic modality of choice.

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Patients with life-threatening hemorrhage require immediate intervention that includes embolization or surgery for better outcome and survival rate.