Epithelioid Angiomyolipoma of the Kidney Mimicking Renal Cell Carcinoma: A Clinicopathologic Analysis of Cases and Literature Review

Epithelioid angiomyolipoma with vascular invasion: An aggressive presentation of an unusual AML variant

Renal angiomyolipoma (AML) is a typically benign renal tumor that is divided into 2 classes, the classical variant and the more aggressive epithelioid variant. It is extremely rare for an AML to exhibit aggressive features such as vascular invasion. We present the case of a 36-year-old female who presented with right lower quadrant pain for 9 months and was found to have an AML with tumor extension into the renal vein and the IVC. Diagnosis was confirmed with histopathology and the patient was treated with a total nephrectomy. The epithelioid subtype of AML is a rare variant that should be considered in the differential of a renal mass with vascular invasion.

Acute haemorrhage from a large renal epithelioid angiomyolipoma: diagnostic and management considerations in a teenage patient with a rare cancer

Acute renal haemorrhage is a life-threatening condition that is complicated in the context of renal malignancy. Here, we present the case of a teenage male presenting acutely with a large, bleeding renal epithelioid angiomyolipoma (EAML) of the kidney-a rare cancer, which is part of the perivascular epithelioid cell tumour family. The patient was managed acutely with prompt resuscitation, transfer to a centre of expertise and haemorrhagic control using radiologically guided endovascular techniques; this subsequently permitted an oncologically sound procedure (radical nephrectomy, inferior vena cava thrombectomy and lymphadenectomy) to be performed within 24 hours. The description and discussion around this unique case summarises the patient's clinical journey, while exploring the current literature surrounding diagnosis and outcomes of patients with renal EAMLs.

Differentiating renal epithelioid angiomyolipoma from clear cell carcinoma: using a radiomics model combined with CT imaging characteristics

PURPOSE

This study aims to assess the computed tomography (CT) findings of renal epithelioid angiomyolipoma (EAML) and develop a radiomics-based model for differentiating EAMLs and clear cell renal cell carcinomas (RCCs).

METHOD

This two-center retrospective study included 28 histologically confirmed EAMLs and 56 size-matched clear cell RCCs with preoperative three-phase kidney CTs. We conducted subjective image analysis to determine the CT parameters that can distinguish EAMLs from clear cell RCCs. Training and test sets were divided by chronological order of CT scans, and radiomics model was built using ten selected features among radiomics and CT features. The diagnostic performance of the radiomics model was compared with that of the three radiologists using the area under the receiver-operating characteristic curve (AUC).

RESULTS

The mean size of the EAMLs was 6.2 ± 5.0 cm. On multivariate analysis, a snowman or ice cream cone tumor shape (OR 16.3; 95% CI 1.7-156.9, P = 0.02) and lower tumor-to-cortex (TOC) enhancement ratio in the corticomedullary phase (OR 33.4; 95% CI 5.7-197, P < 0.001) were significant independent factors for identifying EAMLs. The diagnostic performance of the radiomics model (AUC 0.89) was similar to those of genitourinary radiologists (AUC 0.78 and 0.81, P > 0.05) and superior to that of a third-year resident (AUC 0.63, P = 0.04).

CONCLUSIONS

A snowman or ice cream cone shape and lower TOC ratio were more closely associated with EAMLs than with clear cell RCCs. A CT radiomics model was useful for differentiating EAMLs from clear cell RCCs with better diagnostic performance than an inexperienced radiologist.

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.

Renal Epithelioid Angiomyolipoma in Children

Renal angiomyolipoma is a rare cause of renal tumor in children. Most are associated with tuberous sclerosis, and the classic type is observed more commonly. Epithelioid angiomyolipoma is even rarer with only limited case reports and series published in literature, most of which are of adult patients. We describe a 12-year-old boy, a diagnosed patient of tuberous sclerosis, who presented with pain in the left flank. On evaluation, it was found to have a left renal mass with the clinical picture suggestive of renal cell carcinoma. Partial nephrectomy was performed and histopathology revealed epithelioid angiomyolipoma. The child was asymptomatic at follow-up after 3 months. Only a few such cases in children are found in literature, which are discussed alongside. Differential diagnosis of this rare tumor must be kept in mind in a renal tumor as surgery is generally curative in this possibly malignant tumor. Metastasis confers a poor prognosis. Chemotherapy is generally not effective, although various regimens have been tried. Tumor recurrence must be kept in mind and a follow-up after apparent complete remission is of paramount importance.

Everolimus in Invasive Malignant Renal Epithelioid Angiomyolipoma

Background

To evaluate the efficacy and safety of everolimus, a mTOR inhibitor, on invasive malignant renal epithelioid angiomyolipoma (EAML).

Materials and Methods

From Oct 2014 to May 2019, we collected data from seven patients with a definite (clinical and pathological) diagnosis of EAML received everolimus in our hospital. Targeted sequence capture array technique with next-generation of high throughput sequencing (NGS) were performed to detect mutations of TSC1/2 genes. All patients had received surgery and everolimus. The clinical efficacy and safety of the therapy were evaluated.

Results

Mutations of TSC1 and TSC2 were detected in two and three patients though targeted sequence capture array technique with NGS, respectively. Among seven patients, three had missense mutations, one had nonsense mutation, and one had the large fragment deletion mutation. Five patients accompanied with tuberous sclerosis complex (TSC) were identified. All patients were administered 10mg everolimus once daily, the treatment duration lasted for 3 to 28 months. The objective response was assessed 3 months later, five partial response, two stable disease (SD), the mean greatest tumor diameter of all patients decreased from 9.6 to 5.2cm. Six patients stayed SD and one patient died during follow up. Patients accompanying with TSC had better responses to everolimus compared with non-TSC.

Conclusion

The mTOR inhibitor can be an effective treatment for patients with invasive malignant renal EAML. Patients with TSC may benefit more from the therapy.

Diagnostic pitfall of a rare variant of angiomyolipoma, epithelioid angiomyolipoma - a case report

Angiomyolipoma of the kidney is a common benign mesenchymal neoplasm of kidney. A rare variant, epithelioid angiomyolipoma, however, may show malignant behavior. We report a case of epithelioid angiomyolipoma in a patient not having tuberous sclerosis which was initially misdiagnosed as renal cell carcinoma. A 39-year-old woman presented with a history of flank pain. Ultrasonography revealed a left renal mass. Contrast-enhanced computed tomography (CECT) abdomen revealed mass involving hilum of the kidney. On core biopsy a possibility of renal cell carcinoma was suggested. The patient underwent radical nephrectomy. After immunohistochemical analysis, a final diagnosis of epithelioid angiomyolipoma was made. Renal epithelioid angiomyolipoma without adipocytic component is extremely rare. It is pivotal to keep a possibility of epithelioid angiomyolipoma whenever an epithelioid renal tumor is encountered showing marked pleomorphism and mitosis. The use of melanocytic markers and specific markers of renal cell carcinoma will aid the diagnosis.

Renal Epithelioid Angiomyolipoma: A Case Report and Review of Literature

Epithelioid angiomyolipoma (EAML) is an uncommon renal neoplasm with malignant potential. It is classified under the group of perivascular epithelioid cell tumors and can be sporadic or as part of the tuberous sclerosis complex. On imaging, unlike classical AML that contains fat, EAML has a very low percentage of fat which can mimic the imaging findings of renal cell carcinoma. We reported a 31-year-old female who had a history of renal failure and bilateral renal masses. Magnetic resonance imaging of the abdomen revealed bilateral large renal masses replacing renal parenchyma with features suggestive of bilateral renal AML. The patient underwent left nephrectomy, and histopathology examination findings were consistent with the diagnosis of EAML.

Malignant renal epithelioid angiomyolipoma with TFE3 gene amplification mimicking renal carcinoma

Malignant renal epithelioid angiomyolipoma (EAML) is an extremely rare disease with a poor prognosis, and currently there are no uniform criteria for its biological behavior. Here, we present a case of malignant renal EAML with TFE3 gene amplification in a 53-year-old woman. Four months after surgery, unenhanced computed tomography scans showed recurrence as well as metastasis in the abdomen and lung. The patient succumbed to rapid neoplastic progression of the disease 6 months later.

Renal Epithelioid Angiomyolipoma Associated with Pulmonary Lymphangioleiomyomatosis: Imaging Findings

Renal angiomyolipomas (AMLs) and pulmonary lymphangioleiomyomatosis (LAM) are the most common tumors of the perivascular epithelioid cell (PEComa) family. Both may be associated with tuberous sclerosis (TS) complex. Epithelioid AML (EAML) is a rare variety of AMLs, with a potential aggressive behavior. There are few reports in the English literature addressing on the imaging findings of renal EAMLs, which are considered nonspecific. We present the sonographic, computed tomographic, and magnetic resonance imaging findings of a renal EAML in a pregnant woman with concomitant pulmonary lesions indicative of LAM, without stigmata of TS. We conclude the importance of considering EAML as a possible diagnosis in the presence of a large renal mass with high cellular content and small amounts of fat in the coexistence of pulmonary LAM.

Selective arterial embolization of symptomatic and asymptomatic renal angiomyolipomas: a retrospective study of safety, outcomes and tumor size reduction

BACKGROUND

Angiomyolipoma (AML) is the most common renal benign tumor. Treatment should be considered for symptomatic patients or for those at risk for complications, especially retroperitoneal bleeding which is correlated to tumor size, grade of the angiogenic component and to the presence of tuberous sclerosis complex (TSC). This study reports our single-center experience with the use of selective arterial embolization (SAE) in the management of symptomatic and asymptomatic renal AMLs.

METHODS

In this retrospective mono-centric study, all demographic and imaging data, medical records, angiographic features, outpatient charts and follow-up visits of patients who underwent prophylactic or emergency SAE for AMLs between January 2005 and July 2016 were reviewed. Tumor size and treatment outcomes were assessed at baseline and after the procedure during follow-up. Computed tomography (CT), magnetic resonance imaging (MRI) or ultrasonography was used to evaluate AML shrinkage. Renal function was measured pre- and post-procedure.

RESULTS

Twenty-three patients (18 females, 5 males; median age, 45 years; range, 19-85 years) who underwent SAE either to treat bleeding AML (n=6) or as a prophylactic treatment (n=17) were included. Overall, 34 AMLs were embolized. TSC status was confirmed for 6 patients. Immediate technical success rate was 96% and 4 patients benefitted from an additional procedure. Major complications occurred in 3 patients and minor post-embolization syndrome (PES) in 14 patients. The mean AML size reduction rate was 26.2% after a mean follow-up was 20.5 months (range, 0.5-56 months), and only non-TSC status was significantly associated with better shrinkage of tumor (P=0.022). Intralesional aneurysms were significantly more frequent in patients with hemorrhagic presentation (P=0.008). There was no change in mean creatinine level after SAE.

CONCLUSIONS

SAE is a safe and effective technique to manage renal AMLs as a preventive treatment as well as in emergency setting, with significant reduction in tumor size during follow-up. A multidisciplinary approach remains fundamental, especially for TSC patients. In addition to size, the presence of intralesional aneurysms should be considered in any prophylactic treatment decision.

Diagnosis of Renal Angiomyolipomas: Classic, Fat-Poor, and Epithelioid Types

With the increasing discovery of small renal masses with cross-sectional imaging, there has been the concomitant rise in their treatment. With the intent of early curative surgery for a presumed renal cell carcinoma, many renal masses are being resected at surgery without a confirmed diagnosis. Many of them are benign, and some are angiomyolipomas. The diagnosis of renal angiomyolipoma using imaging is, therefore, is as important as ever. Although most, if not all angiomyolipomas with abundant fat are diagnosed readily, some have too little fat to be detected with imaging. This article reviews the current classification, imaging pitfalls, and diagnosis of angiomyolipoma with an emphasis on the fat-poor types. Proper imaging technique, a thorough search for fat, and the appropriate use of percutanoeus biopsy are all needed to eliminate the unnecessary treatment of these benign neoplasms.

Histotype differentiation of hypo-echoic renal tumors on CEUS: usefulness of enhancement homogeneity and intensity

PURPOSE

The purpose of this study is to evaluate qualitative and quantitative analysis of contrast-enhanced ultrasound (CEUS) in differential diagnoses of hypo-echoic renal tumor histotypes.

METHODS

Our study cohort comprised 103 clear cell renal cell carcinomas (ccRCCs), 24 papillary renal cell carcinomas (pRCCs), 28 chromophobe renal cell carcinomas (cRCCs), and 34 angiomyolipomas (AMLs), hypo-echoic on ultrasound, and imaged between January 2011 and December 2013. Enhancement homogeneity and tumor-to-cortex intensity ratio (TOC ratio) were retrospectively analyzed.

RESULTS

Overall, heterogeneous enhancement was more common in ccRCCs than AMLs, pRCCs, and cRCCs. TOC ratio showed the trend ccRCC > AML > pRCC = cRCC. Similar trends were seen in tumors <4 cm. Using heterogeneous enhancement or TOC ratio >107.5% to differentiate ccRCC from other histotypes, the sensitivity, specificity, positive and negative predictive values were 93.1%, 74.5%, 84.8%, and 87.5%, respectively. Tumors >4 cm exhibited considerable overlap in enhancement homogeneity among different histotypes. TOC ratios were similar between homo- and heterogeneously enhancing tumors for ccRCCs and for pRCCs and cRCCs, but higher in homogeneously enhancing than heterogeneously enhancing AMLs. In homo- and heterogeneously enhancing tumors, TOC ratios followed the trends ccRCCs > AMLs > pRCCs = cRCCs and ccRCCs > AMLs = pRCCs = cRCCs, respectively. With TOC ratio >105.81% and >72.37% to differentiate homo- and heterogeneously enhancing ccRCCs from other histotypes in tumors >4 cm with same enhancement homogeneity, the sensitivity, specificity, positive and negative predictive values were 70.0%, 85.7%, 70.0%, 85.7%, and 91.7%, 94.4%, 95.7%, 89.5%, respectively.

CONCLUSION

CEUS homogeneity and TOC ratio are helpful in differential diagnosis of hypo-echoic renal tumor histotypes. Diameter and enhancement homogeneity should be considered when deciding the diagnostic TOC ratio cutoff.

Quantitative evaluation of contrast-enhanced ultrasound for differentiation of renal cell carcinoma subtypes and angiomyolipoma

PURPOSE

To investigate the value of quantitative parameters of contrast-enhanced ultrasound (CEUS) in the differentiation of subtypes of renal cell carcinoma (RCC) and angiomyolipoma (AML).

METHODS

The quantitative characteristics of 341 RCCs and 88 AMLs were analyzed with quantitative software (SonoLiver). Quantitative analysis was conducted in the whole tumor (ROItumor) and the maximum enhanced area of the tumor (ROImax), acquiring the parameters of maximum intensity (IMAX), rise time (RT), time to peak (TTP), mean transit time (mTT), and area under the curve (AUC), were derived and analyzed. The difference values between ROImax and normal renal cortex (ΔPar.s, including ΔIMAX, ΔRT, ΔTTP, ΔmTT, ΔAUC) were compared among renal histotypes.

RESULTS

All time-related parameters (including RT, TTP and mTT) of ROImax were shorter than the corresponding parameters of ROItumor in RCC subtypes (all p<0.05), but made no statistical difference in AMLs (all p>0.05). There were significant differences of all ΔPar.s among RCC subtypes and AML (all p<0.01). ΔIMAX and ΔAUC showed the trend that ccRCC>AML>pRCC=chRCC. ΔTTP showed AML=pRCC=chRCC>ccRCC, ΔRT and ΔmTT showed AML>pRCC=chRCC=ccRCC. ΔmTT could distinguish RCC from AML with the area under the ROC curve (AUC) of 0.86. The AUC of ΔIMAX and ΔAUC was 0.89 and 0.92 vs 0.85 and 0.85 for discriminating between pRCC (or chRCC) and AML vs ccRCC and AML.

CONCLUSIONS

Quantitative analysis of CEUS is a useful modality in AML and RCC subtypes' differentiation, by using ΔmTT, ΔIMAX and ΔAUC.

Malignant renal epithelioid angiomyolipoma: A case report and review of the literature

Malignant renal epithelioid angiomyolipoma (EAML) is rare, and currently there is no malignant criteria for its pathological diagnosis. In the present study, the case of a patient who suffered malignant renal EAML and underwent nephrectomy is reported. The histological patterns of the tumor were composed of sheets or nests of large polygonal epithelioid cells and thick-walled blood vessels, with clear mitoses. Immunohistochemistry demonstrated that the epithelioid and smooth muscle cells characteristically expressed human melanoma black-45, epithelial membrane antigen and actin. Pathological evaluation revealed malignant EAML with regional lymph node metastases. Magnetic resonance imaging and X-ray examination identified multiple liver and lung nodules at 16 months post-surgery. Since the patient did not respond to the initial treatment with doxorubicin and cisplatin, sorafenib was subsequently administered. However, the treatment was not effective, and the patient succumbed to multiple metastases six months later.

Triphasic and epithelioid minimal fat renal angiomyolipoma and clear cell renal cell carcinoma: qualitative and quantitative CEUS characteristics and distinguishing features

PURPOSE

To determine the contrast-enhanced ultrasonography (CEUS) characteristics of minimal fat renal angiomyolipoma (AML) (triphasic and epithelioid) and compare them to each other and to clear cell renal cell carcinoma (ccRCC) to explore their differential diagnostic clue.

METHODS

Qualitative and quantitative CEUS analyses were retrospectively conducted for epithelioid renal AMLs (EAMLs) (n = 15), triphasic minimal fat AMLs (TAMLs) (n = 25), and ccRCCs (n = 113). Enhancement patterns and features with CEUS were qualitatively evaluated. As for the quantitative parameters, rise times (RT), time to peak (TTP), and tumor-to-cortex enhancement ratio (TOC ratio) were compared among these renal tumor histotypes.

RESULTS

No significant differences were detected on conventional ultrasound in the three histotypes of renal tumor. On qualitative CEUS analysis, centripetal enhancement in cortical phase (73.3% in EAMLs, 84.0% in TAMLs vs. 18.6% in ccRCCs, p < 0.001 for both), homogeneous peak enhancement (100.0% in both EAMLs and TAMLs vs. 43.4% in ccRCCs, p < 0.001 for both), and iso-enhancement in parenchyma phase (53.3% in AMLs, 52.0% in TAMLs vs. 26.5% in ccRCCs, p = 0.034 and 0.013, respectively) were valuable traits for differentiating EAMLs and TAMLs from ccRCCs. Furthermore, with quantitative analysis, RT and TTP were much shorter in ccRCCs than those in EAMLs and TAMLs. However, all these qualitative and quantitative characteristics made no significant difference between EAMLs and TAMLs. In the differential diagnosis of EAMLs from TAMLs, pseudocapsule sign was valuable (40.0% in EAMLs vs. 0.0% in TAMLs, p < 0.001), and TOC ratio was much higher in EAMLs (166.01 ± 64.47%) than that in TAMLs (93.74 ± 46.56%)(p < 0.001), though they did make overlaps with ccRCCs. With either heterogeneous peak enhancement or the presence of pseudocapsule or TOC ratio >97.34% as the criteria to differentiate ccRCCs and EAMLs from TAMLs, the sensitivity and specificity were 80.0% and 87.5%, respectively.

CONCLUSIONS

Qualitative and quantitative CEUS analyses are helpful in the differential diagnosis of ccRCCs, EAMLs, and TAMLs.

CT-imaging features of renal epithelioid angiomyolipoma

Background

The aim of this study was to describe the computed tomography (CT)-imaging features of renal epithelioid angiomyolipomas (E-AMLs) to understand and recognize this new category of renal tumors.

Methods

Institutional review board approval was obtained for this retrospective study. Clinical data and preoperative CT images of 11 cases of E-AML were retrospectively analyzed. All patients had unenhanced and tri-phase dynamic enhanced CT examination. CT-imaging features including tumor size, existence of fat and calcification, enhancement degree, enhancement pattern, and enhancement heterogeneity were evaluated.

Results

The patients were ten women and one man. The size of tumor ranged from 1.8 to 10.3 cm. All of them had distinct edges; one had a lobulated appearance, ten had bulging contour of the involved kidney, and four lesions had intratumoral fat. Eight of the E-AMLs demonstrated hyper-attenuation, two as iso-attenuation, and one as hypo-attenuation compared with renal parenchyma on unenhanced CT images. Contrast-enhanced CT features were markedly heterogeneous in eight cases (73 %). The predominant enhancement pattern was rapid wash-in to slow wash-out (91 %).

Conclusions

The radiological appearance of most E-AMLs has a tendency to be hyper-attenuated on precontrast CT with or without fat component and demonstrates a rapid wash-in to slow wash-out dynamic enhancement pattern.

Fat-poor angiomyolipoma with cyst-like changes mimicking a cystic renal cell carcinoma: a case report

Angiomyolipoma is a common benign renal tumor. It is typically composed of adipose tissue and hence is easily diagnosed by using imaging methods such as ultrasonography, computed tomography, and magnetic resonance imaging. However, it is difficult to differentiate an atypical angiomyolipoma such as a fat-poor angiomyolipoma from a malignant tumor by using these imaging methods. We report a case of a fat-poor angiomyolipoma with cyst-like changes in a 35-year-old man. The angiomyolipoma was initially suspected to be a cystic renal cell carcinoma according to preoperative imaging studies. A 5-cm cystic tumor with an enhanced septal wall and exophytic formation was present in the middle section of the left kidney. The patient underwent partial nephrectomy. Pathological findings showed necrosis and hematoma in almost the entire lesion, with a small amount of adipose and muscle tissue. Finally, a fat-poor angiomyolipoma was diagnosed.

A Four-Year Follow-up Study of Renal Epithelioid Angiomyolipoma: A Multi-Center Experience and Literature Review

In this study, we systematically explored the clinical manifestations, diagnosis, treatment, and prognosis of renal epithelioid angiomyolipoma (EAML) retrospectively by analyzing data of 52 patients diagnosed with EAML at four centers. Our results showed that the onset of EAML was usually inconspicuous, and so no obvious symptoms or signs had occurred in most patients at diagnosis. Its diagnoses always depended on postoperative pathological examination. The immunohistochemical (IHC) results [HMB45 ( + ), cytokeratin (-), and S100 (-)] could be used to differentiate EAML from other malignancies such as renal cell cancer (RCC) and sarcomas. For treatment, surgery resulted in satisfactory short-term prognosis. The long-term prognosis of patients with EAML was poor, particularly when a large size, a high percentage of epithelioid component, tumor thrombus formation, and necrosis were present. In conclusion, EAML is a tumor with malignant potential. Once diagnosed, integrated approaches, including surgery, chemotherapy, and targeted therapy, should be considered; a close follow-up regimen is necessary for cases that met: 1) tumor size >9 cm, 2) tumor thrombus formation in the vein, 3) epithelioid cells >70% or atypia cells >60%, and 4) necrosis.

Qualitative and quantitative analysis with contrast-enhanced ultrasonography: diagnosis value in hypoechoic renal angiomyolipoma

Objective

To evaluate the value of enhancement features and quantitative parameters of contrast-enhanced ultrasonography (CEUS) in differentiating solid hypoechoic renal angiomyolipomas (AMLs) from clear cell renal cell carcinomas (ccRCCs).

Materials and Methods

We analyzed the enhancement features and quantitative parameters of CEUS in 174 hypoechoic renal masses (32 AMLs and 142 ccRCCs) included in the study.

Results

Centripetal enhancement pattern was more common in AMLs than in ccRCCs on CEUS (71.9% vs. 23.2%, p < 0.001). At peak enhancement, all AMLs showed homogeneous enhancement (100% in AML, 27.5% in ccRCCs; p < 0.001). Quantitative analysis showed no significant difference between rise time and time to peak. Tumor-to-cortex (TOC) enhancement ratio in AMLs was significantly lower than that in ccRCCs (p < 0.001). The criteria of centripetal enhancement and homogeneous peak enhancement together with TOC ratio < 91.0% used to differentiate hypoechoic AMLs from ccRCCs resulted in a sensitivity and specificity of 68.9% and 95.8%, respectively.

Conclusion

Both qualitative and quantitative analysis with CEUS are valuable in the differential diagnosis of hypoechoic renal AMLs from ccRCCs.

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

Angiomyolipoma is the most common benign solid renal neoplasm observed in clinical practice. Once thought to be a hamartoma and almost always diagnosed by the imaged-based detection of fat, angiomyolipomas are now known to consist of a heterogeneous group of neoplasms. Although all are considered perivascular epithelioid cell tumors, many display different pathology, imaging features, and clinical behavior. The importance of understanding this group of neoplasms is emphasized by the fact that many types of angiomyolipoma contain little to no fat, and despite being benign, sometimes escape a pre-operative diagnosis. These types of angiomyolipomas can all be considered when encountering a renal mass that is both hyperattenuating relative to renal parenchyma on unenhanced CT and T2-hypointense, features that reflect their predominant smooth muscle component. We review recent developments and provide a radiological classification of angiomyolipomas that helps physicians understand the various types and learn how to both diagnose and manage them.

Renal sinus fat invasion and tumoral thrombosis of the inferior vena cava-renal vein: only confined to renal cell carcinoma

Epithelioid angiomyolipoma (E-AML), accounting for 8% of renal angiomyolipoma, is usually associated with tuberous sclerosis (TS) and demonstrates aggressive behavior. E-AML is macroscopically seen as a large infiltrative necrotic tumor with occasional extension into renal vein and/or inferior vena cava. However, without history of TS, renal sinus and venous invasion E-AML would be a challenging diagnosis, which may lead radiologists to misinterpret it as a renal cell carcinoma (RCC). In this case presentation, we aimed to report cross-sectional imaging findings of two cases diagnosed as E-AML and pathological correlation of these aforementioned masses mimicking RCC.

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

Angiomyolipoma is the most common benign solid renal neoplasm observed in clinical practice. Once thought to be a hamartoma and almost always diagnosed by the imaged-based detection of fat, angiomyolipomas are now known to consist of a heterogeneous group of neoplasms. Although all are considered perivascular epithelioid cell tumors, many display different pathology, imaging features, and clinical behavior. The importance of understanding this group of neoplasms is emphasized by the fact that many types of angiomyolipoma contain little to no fat, and despite being benign, sometimes escape a pre-operative diagnosis. These types of angiomyolipomas can all be considered when encountering a renal mass that is both hyperattenuating relative to renal parenchyma on unenhanced CT and T2-hypointense, features that reflect their predominant smooth muscle component. We review recent developments and provide a radiological classification of angiomyolipomas that helps physicians understand the various types and learn how to both diagnose and manage them.

Angiomyolipoma of the kidney: clinicopathological and immunohistochemical study

OVERVIEW

Although angiomyolipoma (AML) is a relatively rare entity, it is the most common benign mesenchymal neoplasm of the kidney.

THE AIM OF THIS STUDY

To highlight the clinicopathological characteristics of AML and to assess the role of Human Melanoma Black-45 (HMB-45), Melan-A, smooth muscle actin (SMA), S-100 and cytokeratin in its diagnosis.

MATERIALS AND METHODS

The study included 15 cases of AML. Clinical and radiological data were retrieved from the archival files and all cases were subjected to a histopathological evaluation as well as immunohistochemical staining for HMB-45, Melan-A, SMA, S-100, and cytokeratin.

RESULTS

AML was more common in females (female:male = 4:1), the mean age was 53.9 ± 6.45 years. 60% of patients were symptomatic while the remaining 40% were asymptomatic. A statistically significant relationship was found between size of the tumor and the presence of the symptoms (P = 0.02). Patients with tumor size less than 4 cm were asymptomatic, while those with tumor size larger than 4 cm had different symptoms. Thirteen cases were classic AML, while 2 cases were epithelioid AML. Classic AML demonstrated admixture of fatty tissue, thick-walled blood vessels, and smooth muscle, while epithelioid AML was composed mainly of epithelioid cells and contained no fat. HMB-45 was positive in all cases of AML (100%), Melan-A was positive in 13/15 (87%) while SMA was positive in 11/15 (73%) of AML with variable staining intensity. All cases of AML were negative for S-100 and cytokeratin.

CONCLUSION

AMLs have characteristic clinicopathological and immunohistochemical features and their recognition is crucial for proper diagnosis and treatment.

Renal epithelioid angiomyolipoma with a negative premelanosome marker immunoprofile: a case report and review of the literature

Introduction

The rare variant of renal epithelioid/pleomorphic angiomyolipoma has been reported in approximately 120 cases. One of the most important characteristics to differentiate these tumors from other renal cell neoplasms is their typical reactivity to premelanosome antigens. If such a tumor does not stain for HMB-45 or Melan-A, a specific diagnosis of epithelioid pleomorphic angiomyolipoma cannot be made with certainty.

Case presentation

We present here what is, to the best of our knowledge, the first case of epithelioid/pleomorphic angiomyolipoma of the kidney in a 50-year-old Caucasian man with no history of tuberous sclerosis, and with a tumor marker profile negative for several premelanosome antigens. The tumor was composed of sheets of pleomorphic, round to polygonal epithelioid cells with prominent eosinophilic cytoplasm, large nuclei, many multinucleated, and very prominent nucleoli. There were prominent vessels and rare interspersed smooth muscle fibers, but adipocytes were not identified. A tumor marker profile showed tumor cell reactivity for CD68, calponin and focally for CD10. Intervening smooth muscle was reactive with smooth muscle actin. The tumor lacked reactivity for melanin-associated antigens HMB-45 and Melan-A, and for CD31, pan-cytokeratin (AE1/3) and desmin. Electron microscopic examination of tumor cells confirmed the presence of premelanosome-like granules.

Conclusions

Based on the characteristic microscopic appearance of this tumor, and its overall tumor marker profile, we concluded this was a renal epithelioid/pleomorphic angiomyolipoma with a negative premelanosome antigen phenotype.

Renal epithelioid angiomyolipoma: imaging characteristics in nine cases with radiologic-pathologic correlation and review of the literature

OBJECTIVE

The purpose of this study was to describe the imaging features of renal epithelioid angiomyolipoma (EAML), a rare subtype of angiomyolipoma, with clinical and pathologic correlation.

MATERIALS AND METHODS

This study was a retrospective review of nine cases from a single institution in which total resection and preoperative imaging were performed and the diagnosis of EAML was made. Imaging included CT (nine cases), MRI (five cases), and ultrasound (one case), and the images were reviewed in consensus by two radiologists. Patient demographics, disease associations, presentation, and outcomes were determined by chart review.

RESULTS

The patients were nine women and one man (mean age, 42 years). Two patients had tuberous sclerosis complex. The size of the nine EAMLs ranged from 1.4 to 22 cm (mean, 7.8 cm). Six lesions had minor components of fat identifiable at imaging. The contrast enhancement pattern was heterogeneous in eight lesions, five of which contained cysts, necrosis, and hematoma. Four presentations were acute hemorrhage, with ruptured EAML in three of the four. Five tumors extended into the renal sinus. Two tumors were locally invasive. One patient had metastatic disease at presentation with epithelioid tumor identified in a single lymph node. The follow-up periods ranged from 0 to 89 months, and there was one case of suspected but not yet proved recurrence.

CONCLUSION

Renal EAML can have a range of imaging appearances and can be indistinguishable from renal cell carcinoma and angiomyolipoma with minimal fat. EAML can be considered when a mass is found that has small foci of macroscopic fat without calcification or when acute hemorrhage of a renal mass occurs.

Epithelioid angiomyolipoma of the kidney: radiological imaging

OBJECTIVES

To review the imaging findings of renal epithelioid angiomyolipomas.

METHODS

Eight patients treated at two institutions were pathologically diagnosed as having epithelioid angiomyolipoma. All of them underwent computed tomography, and four underwent magnetic resonance imaging. The tumor size, existence of fat, heterogeneity, computed tomography attenuation, degree of enhancement, enhancement pattern and magnetic resonance imaging signal intensity were evaluated.

RESULTS

Intratumoral fat was not detected in any of the cases. On unenhanced computed tomography, the intratumoral attenuation was hyperattenuating in six of the seven patients who were examined using this modality. On T2-weighted images, the signal intensity of the solid component, cyst wall or septum was low in three of the four cases. Four of the eight cases were heterogeneous solid-type accompanied by hemorrhage, necrosis or hyalinization. One homogeneous solid-type lesion was large in size and was pathologically accompanied by neither hemorrhage nor necrosis. All three multilocular cystic types were pathologically accompanied by massive hemorrhage in the cystic component. One was accompanied by spontaneous perirenal hematoma.

CONCLUSIONS

The radiological appearance of most epithelioid angiomyolipomas has a tendency to be hyperattenuating on unenhanced computed tomography images, with low intensities on T2-weighted images. They can be heterogeneously solid, homogeneously solid or a multilocular cystic lesion with massive hemorrhage.

Minimal fat renal angiomyolipoma: the initial study with contrast-enhanced ultrasonography

We visualized minimal fat renal angiomyolipomas (AMLs) by contrast-enhanced ultrasonography (CEUS). Conventional ultrasound and CEUS images were retrospectively analyzed for solid minimal fat renal AML cases (n = 18) and solid renal cell carcinoma (RCC) cases (n = 105). We compared size, echogenicity and color flow signals with conventional ultrasound, and enhancement patterns with CEUS, in AMLs vs. RCCs. No significant differences in echogenicity and color flow signal existed between AMLs and RCCs using conventional ultrasound. With CEUS, slow centripetal enhancement in the cortical phase (83.3% of AMLs vs. 1.9% of RCCs) and homogeneous peak enhancement (100.0% of AMLs vs. 34.3% of RCCs) were valuable traits for differentiating these tumor types. These two CEUS-determined traits, combined, were differentiating criteria for minimal fat renal AMLs and RCCs; positive and negative predictive values were 100.0% and 97.2%, respectively. Slow centripetal enhancement in the cortical phase and homogeneous enhancement at peak are main features of CEUS-confirmed solid minimal fat renal AML.

Clinicopathological analysis of 156 patients with angiomyolipoma originating from different organs

Angiomyolipoma (AML) is a benign mesenchymal tumor composed of variable proportions of adipose tissue, spindle and epithelioid smooth muscle cells and abnormal thick-walled blood vessels. Approximately one-third of epithelioid AML (EAML) cases have been reported to have metastasis. Thus, it would be of interest to identify the adverse pathological parameters correlated with outcome. However, few studies have been conducted on large numbers of samples. The aim of this study was to highlight the clinicopathological features of AML and the morphological features of EAML, which were correlated with malignant behaviors in patients from a single institutional series analysis. One hundred and fifty-six consecutive AMLs, correlating with pathological characteristics, were analyzed between 1981 and 2010. The Chi-square test was performed to clarify the significance of the clinicopathological factors among the regular and epithelioid subtypes with or without atypia. The two organs most commonly involved were the kidney (77%, 120/156) and liver (14%, 22/156). Of the 156 AMLs, EAMLs (17.3%, 27/156) had more marked mitosis, hemorrhage and multinucleated giant cells compared with the regular AMLs (82.7%, 129/156). The 11 EAMLs with atypia (40.7%, 11/27) had more nucleoli and mitotic cells compared with the 16 EAMLs without atypia (59.3%, 16/27; p<0.05). Follow-up results of 79% of cases (124/156) were obtained, and of these, only one kidney AML (0.8%, 1/124) presented with liver metastasis one year after nephrectomy. This sizeable single institutional AML series analysis revealed that the kidney and liver were the two most commonly involved organs, and most of the cases presented a benign clinical course. Few EAMLs were malignant, although adverse features including atypical mitotic figures, blood vessel invasion and tumor embolus may be significant in predicting malignant behavior.

A massive renal epithelioid angiomyolipoma with multiple metastatic lymph nodes

A 47-year-old man presented with dull pain in the left upper abdomen for 1 year. Computed tomograph (CT) examination revealed a very large heterogeneously enhancing mass in the left kidney, measuring up to 28 cm. The mass was accompanied by several enlarged lymph nodes in the peri-aortic region. Radical nephrectomy was performed and pathologic evaluation revealed sheets of epithelioid cells and piecemeal necrosis consistent with malignant epithelioid angiomyolipoma (EAML) with regional lymph node metastases. The tumor cells were strongly positive for human melanosome-associated protein (HMB-45) on immunohistochemical staining. There was neither metastasis nor recurrence 2 years postoperatively. EAML is a rare tumor of mesenchymal tissue with potential for aggressive behavior. If this neoplasm is suspected based on CT features, EAML should be confirmed by pathology and immunohistochemistry.

The radiological diagnosis and treatment of renal angiomyolipoma-current status

Angiomyolipomas (AMLs) are the most common benign renal neoplasm and are often discovered incidentally. Due to both an increase in the use of imaging, as well as advances in imaging technology, they are being increasing identified in the general population. As these lesions are benign, there is good evidence that the majority of them can be safely followed up without treatment. However, there is an increasing wealth of information available suggesting there are individuals with AMLs where prophylactic treatment is indicated to prevent complications such as haemorrhage. In such cases, treatment with radiological interventional techniques with subselective particle embolization has superseded surgical techniques in most cases. Even in emergency cases with catastrophic rupture, prompt embolization may save the patient with the additional benefit of renal salvage. Confident identification of a lesion as an AML is important as its benign nature obviates the need for surgery in most cases. The presence of fat is paramount in the confirmatory identification and characterization of these lesions. Although fat-rich AMLs are easy to diagnose, some lesions are fat poor and it is these cases where newer imaging techniques, such as in-phase and out-of-phase magnetic resonance imaging (MRI) may aid in making a confident diagnosis of AML. In this paper, we comprehensively review the imaging techniques in making a diagnosis of AML, including features of both characteristic lesions as well as atypical lesions. In addition, we discuss current guidelines for follow-up and prophylactic treatment of these lesions, as well as the increasing role that the interventional radiologist has to play in these cases.