Renal epithelioid angiomyolipoma: magnetic resonance imaging characteristics

OBJECTIVE

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

METHODS

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

RESULT

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

CONCLUSION

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

Surveillance imaging for sporadic renal angiomyolipoma less than 40 mm: lessons learnt and recommendations from the experience of a large district general hospital

Introduction Sporadic renal angiomyolipomas, although benign in natural can cause life-threatening spontaneous haemorrhage. Surveillance of smaller lesions is recommended but there is no guidance on the surveillance interval or modality. Our aim was to study our sporadic angiomyolipoma population to determine the growth rate, factors that were associated with a higher growth rate and design a surveillance programme. Materials and methods All sporadic renal angiomyolipomas diagnosed between September 2009 and March 2015 were included. Patients with a diagnosis of tuberous sclerosis were excluded. Results A total of 217 sporadic renal angiomyolipomas were diagnosed. The median follow-up was 24 months (range 10-118 months). The median size at diagnosis was 9.00 mm with a mean growth rate of 0.13 mm/year (standard deviation 0.88). One hundred and fifty angiomyolipomas (69%) were shown to have negative or zero growth. In the remaining 67, 59 had a growth rate of less than 2.00 mm/year. Size of angiomyolipoma, tumour burden and age were not associated with a higher growth rate on multivariate analysis. Conclusion The majority of sporadic angiomyolipomas are small and do not grow. Our practice is to perform surveillance for those greater than 20 mm, with five-yearly ultrasound scans for 21-29 mm, and two-yearly surveillance for 30-39 mm tumours.

Outcomes of ultrasound guided renal mass biopsies

PURPOSE

The purpose of this study was to evaluate the rate of nondiagnostic ultrasound-guided renal mass biopsies (RMBs) at our institution and to determine what patient, procedural, and focal renal mass (FRM) factors were associated with nondiagnostic ultrasound-guided RMBs.

METHODS

Eighty-two ultrasound-guided renal mass biopsies performed between January 2014 and October 2016 were included in our study. Biopsy outcomes (diagnostic vs. nondiagnostic) and patient, procedural, and FRM characteristics were retrospectively reviewed and recorded. Univariate statistical analyses were performed to identify biopsy characteristics that were indicative of nondiagnostic biopsy.

RESULTS

Ultrasound-guided RMBs were diagnostic in 70 out of 82 cases (85%) and non-diagnostic in 12 cases (15%). Among the diagnostic biopsies, 54 (77%) were malignant cases, 94% of which were renal cell carcinoma (RCC). Of the 12 nondiagnostic cases, the final diagnosis was RCC in 4 cases and angiomyolipoma in one case; seven of the nondiagnostic cases were lost to follow-up. A weak association (p = 0.04) was found between the number of needle passes and the biopsy outcome. None of the remaining collected RMB characteristics showed a significant correlation with a diagnostic or nondiagnostic RMB. Six patients (7%) experienced complications.

CONCLUSION

Ultrasound-guided renal mass biopsy is a safe and effective method for the diagnosis of renal masses with a low rate of nondiagnostic outcomes. A nondiagnostic biopsy should not be treated as a surrogate for a diagnosis since a significant number of patients with nondiagnostic biopsies have subsequently been shown to have renal malignancies. Repeat biopsy should be considered in such cases.

Morphologic analysis with computed tomography may help differentiate fat-poor angiomyolipoma from renal cell carcinoma: a retrospective study with 602 patients

PURPOSE

To assess whether morphologic analysis using computed tomography (CT) could differentiate between fat-poor angiomyolipoma (fpAML) and renal cell carcinoma (RCC).

METHODS

A total of 602 patients with a histologically confirmed fpAML (n = 49) or RCC (n = 553) were evaluated. All renal lesions were less than 4 cm in size and had no gross fat on contrast-enhanced CT. For morphologic analysis, overflowing beer sign and angular interface were evaluated. Overflowing beer sign was defined as contact length between bulging-out portion of a mass and the adjacent renal capsule of 3 mm or greater. Angular interface was defined as the angle of parenchymal portion of a mass of 90° or less. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were assessed. Multivariate analysis was conducted to determine which variable is predictive of fpAML.

RESULTS

Sensitivity, specificity, PPV, NPV, and accuracy were 61.2% (30/49), 97.1% (537/553), 65.2% (30/46), 96.6% (537/556), and 94.2% (567/602) with overflowing beer sign, while they were 55.1% (27/49), 81.9% (453/553), 21.3% (27/127), 95.4% (453/475), and 79.7% (480/602) with angular interface for fpAML, respectively. Both CT variables were predictive of fpAML (overflowing beer sign, odds ratio = 132.881, p < 0.001; angular interface, odds ratio = 5.766, p = 0.010). The multivariate model with CT variables showed good performance for predicting fpAML (AUC, 0.871 with angular interface, 0.943 with overflowing beer sign, and 0.949 with both).

CONCLUSION

Morphologic analysis with contrast-enhanced CT may be useful for differentiating fpAML from RCC. Overflowing beer sign has the potential as an imaging biomarker for fpAML.

[New approach to diagnosis, immunophenotypic verification and prognostic prediction for renal angiomyolipoma]

Renal angiomyolipoma (AML) is a rare benign neoplasm of mesenchymal origin. AML incidence varies from 0.3 to 5%, while women suffer four times more often than men. In most cases, renal AML measures less than 4 cm, is asymptomatic and detected accidentally with computed tomography or ultrasound. A histological variant of AML need to be verified to choose management strategy and reduce the risk of complications. Histological and immunohistochemical assessment of biopsy and surgical specimens has an essential diagnostic value in determining the type and subtypes of renal neoplasms and the risk of malignancy. The study aimed to investigate pathomorphological and prognostic features (immunohistochemical characteristics) of renal AML.

MATERIALS AND METHODS

Patients (n=42) with CT-detected renal neoplasms underwent partial nephrectomy. The majority (n=34) of patients was admitted to the hospital urgently, often without symptoms (n=23). The surgical specimens studied were examined using light microscopy and immunohistochemistry analysis with primary mouse monoclonal antibodies to HMB-45, Melan-A, -SMA, S-100 and SC (Novocastra, UK).

RESULTS

All specimens showed morphological characteristics typical of AML and a positive response to antibodies against HMB-45 (ve +/3; 99.6+/-0.3%), Melan-A (ve + / 2, 89.6+/-4.3%) and SMA (ve + 2; 70.1+/-2.9%) and exhibited no staining with antibodies against S-100 and SK.

CONCLUSION

Morphological study of renal AML shows that the tumor is benign, therefore partial nephrectomy, in our opinion, should be considered as an alternative to radical nephrectomy, including for sporadic giant renal AML.

[A Case of Bilateral Angiomyolipoma Accompanied by Tuberous Sclerosis Complex Successfully Treated with Transcatheter Arterial Embolization Using Functional Kidney Mapping Images Consisting of SPECT-CT and Contrast Enhanced CT Images]

Renal angiomyolipoma (AML) and aneurysm are common in tuberous sclerosis complex (TSC) and represent the main causes of morbidity in adults with TSC. Herein, we report a 22-year-old woman with TSC-associated AMLs and renal aneurysms. She was referred to our hospital for the treatment of multiple renal aneurysms larger than 5 mm in diameter. The previous hospital considered that transcatheter arterial embolization (TAE) of bilateral renal aneurysms would cause deterioration of renal function. To estimate the impact of TAE on renal function, we superimposed contrast enhanced computed tomography (CT) over single-photon emission CT (SPECT)-CT. This fusion image, referred to as functional kidney mapping image, revealed the location of renal arteries and aneurysms, and normal renal parenchyma simultaneously. Functional kidney mapping image was useful to distinguish the AML region from the normal renal parenchyma, and revealed that the planned embolization site was a non-functioning parenchyma. Therefore, TAE for her multiple renal aneurysms was successfully performed without deterioration of her renal function.

Imaging appearance of renal epithelioid angiomyolipoma: A case report and literature review

RATIONALE

Epithelioid angiomyolipoma (EAML) is an extremely rare disease. It commonly occurs in middle-aged females and mainly involves the kidney. Histological and immunohistochemical examination play important roles in differentiating EAML from renal cell carcinoma (RCC) and poor-fat angiomyolipoma (AML).

PATIENT CONCERNS

Here, We report the imaging phenotype, as well as the pathological findings of a case of EAML in a 39-year-old female.

DIAGNOSES

Preoperative noncontrast computed tomography (CT) scan revealed a 6.0 × 5.2 × 7.0 cm soft tissue mass with necrosis, located in the left kidney. On contrast-enhanced CT images, aprogressive enhancement pattern was observed. CT angiography did not show any enlarged vessels or vascular malformation. Abdominal MRI showed a well-circumscribed solid mass with a heterogeneous signal on T1-weighted and T2-weighted images. Ultrasonography of the abdomen demonstrated a hypoechoic mass with abundant blood flow. This patient underwent radical nephrectomy. The pathologic diagnosis was EAML.

INTERVENTIONS

This patient underwent operative resection of the tumor. The resection margins were negative for the neoplastic proliferation and no distant metastases were found. The patient did not receive advanced radiotherapy or chemotherapy.

OUTCOMES

Four months after surgery, the follow-up CT scan did not reveal any local recurrence or distant metastases.

LESSONS

This case adds to the experience with EAML by summarizing its imaging characteristics as well as reviewing the literature. Additionally, we described the state-of-the-art management of the management of this rare tumor.

Bilateral Giant Renal Angiomyolipoma in a Patient with Tuberous Sclerosis Complex: A Case Report

Tuberous sclerosis complex (TSC) has several renal manifestations including angiomyolipomas (AML) and renal epithelial neoplasms. A bilateral giant renal AML is extremely rare. We report a case of giant bilateral AML and discuss the diagnosis and treatment of it. The 22-year-old man was admitted due to bilateral flank pain, gross hematuria, and abdominal fullness. He had history of epilepsy, mental retardation, and delayed development during childhood. He had angiofibroma on his face since 10 years ago. Abdominal CT and MRI revealed large lobulated heterogeneous mass with fatty content. Based on those findings, we diagnosed the patient with bilateral giant renal AML. We gave conservative management for the patient and planned to total nephrectomy on the left kidney if the continued bleeding occurred. AML associated with TSC occur more frequently as multiple lesions and grows to larger size than idiopathic AML. Bilateral giant AML, which is very rare, could be treated with conservative management if no significant hemorrhage occurred.

Treatment effect of mTOR-inhibition on tissue composition of renal angiomyolipomas in tuberous sclerosis complex (TSC)

Purpose

Tuberous sclerosis complex (TSC)-associated renal angiomyolipoma (AML) have a high lifetime risk of acute bleeding. MTOR-inhibitors are a promising novel treatment for TSC-AML, however adequate response to therapy can be difficult to assess. Early changes in MRI signal may serve as a novel early indicator for a satisfactory response to mTOR-inhibitor therapy of AML.

Materials and methods

Thirty-eight patients with the definite diagnosis of tuberous sclerosis receiving everolimus therapy and n = 19 patients without specific therapy were included. 1.5 Tesla MRI was performed including sequences with a selective fat suppression. Patients were investigated prior to the initiation of therapy (baseline) and after <3 months (n = 21 patients), 3 to 6 months (n = 32) and 18 to 24 months (n = 28). Signal and size changes of renal AMLs were assessed at all different timepoints. Signal-to-noise-ratio (SNR), contrast-to-noise-ratio (CNR) and size of angiomyolipomas were evaluated.

Results

Signal changes in 273 AMLs were evaluated. A significant and strong decrease of the CNR of AMLs following the initiation of therapy was measured in the fat-suppressed MR sequence at all time points, compared to the baseline: From 7.41±6.98 to 3.84±6.25 (p ≤ 0.05p = 0.002), 3.36±6.93 (p<0.0001), and 2.50±6.68 (p<0.0001) after less than 3 months, 3–6 months or 18–24 months of everolimus treatment, respectively. Also, a significant, however less pronounced, reduction of angiomyolipoma size in the different groups was measured (from baseline 2022.2±2657.7 mm2 to 1854.4±1670.9 mm2 (p = 0.009), 1875.5±3190.1 mm2 (p<0.001), and 1365.8 ± 1628.8 mm2 (p<0.0001) after less than 3 months, 3–6 months or 18–24 months of everolimus treatment, respectively). No significant changes in CNR (p>0.05) and size (p>0.05) were measured in the control group.

Conclusion

mTOR inhibitor therapy in TSC patients results in an early and pronounced fatty transformation of AMLs on MRI. Fatty transformation could represent a novel early indicator of response to therapy in this patient collective.

Renal Angiomyolipoma With Incidental Oncocytoma: A Case Report and Review of Literature

We present a 37-year-old female with a history of tuberous sclerosis. She developed flank pain, hypotension, and a sudden drop in hemoglobin levels which prompted a work-up. A computed tomography scan demonstrated enlarged heterogeneous kidneys and a large complex collection in the right kidney, likely hemorrhagic in nature. The findings were suspicious for bilateral angiomyolipomas with retroperitoneal hematoma. She was treated with bilateral transarterial embolization. She subsequently developed recurrent fever and was suspected of having emphysematous pyelonephritis, for which she underwent a right nephrectomy. The entire kidney was replaced by a tan bulging, lobular mass, with scattered tan-yellow nodules. Microscopic examination revealed an angiomyolipoma with an incidental oncocytoma. The association of renal angiomyolipoma and renal oncocytoma is rare and only 16 cases have been previously reported.

Sarcomatoid Renal Cell Carcinoma and Collecting Duct Carcinoma: Discrimination From Common Renal Cell Carcinoma Subtypes and Benign RCC Mimics on Multiphasic MDCT

RATIONALE AND OBJECTIVES

To investigate whether imaging features on multiphasic multidetector computed tomography (MDCT) can help discriminate sarcomatoid renal cell carcinoma (RCC) and collecting duct carcinoma (CDC) from other solid renal masses.

MATERIALS AND METHODS

With institutional review board approval for this HIPAA-compliant study, we derived a cohort of 7 sarcomatoid RCCs, 4 CDCs, 165 clear cell RCCs, 56 papillary RCCs, 22 chromophobe RCCs, 49 oncocytomas, and 16 lipid-poor angiomyolipomas with preoperative multiphasic MDCT with up to four phases (unenhanced, corticomedullary, nephrographic, and excretory). Each lesion was reviewed for contour, spread pattern, pattern of enhancement, neovascularity, and calcification.

RESULTS

Sarcomatoid RCCs and CDCs were more likely than other solid renal masses to have an irregular contour (64% vs 2%, P < 0.001) and an infiltrative spread pattern, defined as infiltration into adjacent renal parenchyma, collecting system, or neighboring structures (82% vs 7%, P < 0.001). When used to discriminate sarcomatoid RCC and CDC from other solid renal masses, an infiltrative spread pattern had a specificity of 93% (287/308) and sensitivity of 82% (9/11), and an irregular contour had a specificity of 98% (303/308) and sensitivity of 64% (7/11).

CONCLUSIONS

Solid renal lesions with an irregular contour or an infiltrative spread pattern are suspicious for sarcomatoid RCC or CDC.

Epithelioid Angiomyolipoma - a case report and review of the literature

Herein we present the case of a 43-year-old female in whom a left renal mass was identified incidentally on imaging performed for staging of a newly diagnosed breast carcinoma. The mass was resected and histologic examination and immunohistochemistry confirmed a diagnosis of epithelioid angiomyolipoma.

Can "Tumor-to-Cortex Echogenicity Ratio" Differentiate Angiomyolipomas from Other Hyper-Echoic Renal Masses

A retrospective study was performed to evaluate the diagnostic value of tumor-to-cortex echogenicity ratio (TCER) in the characterization of hyper-echoic renal masses. The radiology database was queried between 2012 and 2014 for hyper-echoic renal masses on the basis of defined exclusion and inclusion criteria. Each included mass was characterized as either an angiomyolipoma (AML) or a non-AML based on pre-defined criteria. The ratio of renal mass echogenicity to that of adjacent renal cortex (TCER) was calculated for each mass using commercially available software. A total of 70 masses in 65 patients were identified, including 49 AMLs. TCER values >2.26 were associated with a sensitivity and specificity of 81.6% and 71.4%, respectively, for diagnosis of AML. Moreover, TCER values >3.98 resulted in 100% specificity for AML diagnosis with a sensitivity of 28.6%. These findings suggest that the TCER may be a valuable tool for the characterization of hyper-echoic renal masses.

CT imaging of solid renal masses: pitfalls and solutions

Computed tomography (CT) remains the first-line imaging test for the characterisation of renal masses; however, CT has inherent limitations, which if unrecognised, may result in errors. The purpose of this manuscript is to present 10 pitfalls in the CT evaluation of solid renal masses. Thin section non-contrast enhanced CT (NECT) is required to confirm the presence of macroscopic fat and diagnosis of angiomyolipoma (AML). Renal cell carcinoma (RCC) can mimic renal cysts at NECT when measuring <20 HU, but are usually heterogeneous with irregular margins. Haemorrhagic cysts (HC) may simulate solid lesions at NECT; however, a homogeneous lesion measuring >70 HU is essentially diagnostic of HC. Homogeneous lesions measuring 20-70 HU at NECT or >20 HU at contrast-enhanced (CE) CT, are indeterminate, requiring further evaluation. Dual-energy CT (DECT) can accurately characterise these lesions at baseline through virtual NECT, iodine overlay images, or quantitative iodine concentration analysis without recalling the patient. A minority of hypo-enhancing renal masses (most commonly papillary RCC) show indeterminate or absent enhancement at multiphase CT. Follow-up, CE ultrasound or magnetic resonance imaging (MRI) is required to further characterise these lesions. Small (<3 cm) endophytic cysts commonly show pseudo-enhancement, which may simulate RCC; this can be overcome with DECT or MRI. In small (<4 cm) solid renal masses, 20% of lesions are benign, chiefly AML without visible fat or oncocytoma. Low-dose techniques may simulate lesion heterogeneity due to increased image noise, which can be ameliorated through the appropriate use of iterative reconstruction algorithms.

Subjective and objective heterogeneity scores for differentiating small renal masses using contrast-enhanced CT

PURPOSE

The aim of this study was to assess the effect of denoising on objective heterogeneity scores and its diagnostic capability for the diagnosis of angiomyolipoma (AML) and renal cell carcinoma (RCC).

MATERIALS AND METHODS

A total of 158 resected renal masses ≤4 cm [98 clear cell (cc) RCCs, 36 papillary (pap)-RCCs, and 24 AMLs] from 139 patients were evaluated. A representative contrast-enhanced computed tomography (CT) image for each mass was selected by a genitourinary radiologist. A largest possible region of interest was drawn on each mass by the radiologist, from which three objective heterogeneity indices were calculated: standard deviation (SD), entropy (Ent), and uniformity (Uni). Objective heterogeneity indices were also calculated after images were processed with a denoising algorithm (non-local means) at three strengths: weak, medium, and strong. Two genitourinary radiologists also subjectively scored each mass independently using a three-point scale (1-3; with 1 the least and 3 the most heterogeneous), which were added to represent the final subjective heterogeneity score of each mass. Heterogeneity scores were compared among mass types, and area under the ROC curve (AUC) was calculated.

RESULTS

For all heterogeneity indices, cc-RCC was significantly more heterogeneous than pap-RCC and AML (p < 0.001), but no significant difference was found between pap-RCC and AML (p > 0.01). For cc-RCC and pap-RCC differentiation, AUCs were 0.91, 0.81, 0.78, and 0.78 for the subjective score, SD, Ent, and Uni, respectively, using original images. The corresponding AUC values were 0.84, 0.74, 0.79, and 0.80 for differentiation of AML and cc-RCC. Noise reduction at weak setting improves AUC values by 0.03, 0.05, and 0.05 for SD, entropy, and uniformity for differentiation of cc-RCC from pap-RCC. Further increase of filtering strength did not improve AUC values. For differentiation of AML vs. cc-RCC, the AUC values stayed relatively flat using the noise reduction technique at different strengths for all three indices.

CONCLUSIONS

Both subjective and objective heterogeneity indices can differentiate cc-RCC from pap-RCC and AML. Noise reduction improved differentiation of cc-RCC from pap-RCC, but not differentiation of AML from cc-RCC.

[Tuberous Sclerosis Complex Detected by Spontaneous Rupture of a Giant Renal Angiomyolipoma : A Case Report]

A woman in her 30s was admitted with abdominal pain and nausea. CT scan revealed a spontaneous rupture of the right giant renal angiomyolipoma, and trans-arterial embolization was performed successfully. With further examination, she was found to be affected with tuberous sclerosis complex (TSC) and she finally wastreated with everolimusfor prevention of recurrent spontaneous-rupture of renal angiomyolipoma.

[A Case of Angiomyolipoma Occurring in the Mesentery of the Transverse Colon and Treated Using Laparoscopic Excision]

A 65-year-old woman had received chemotherapy for malignant lymphoma since 2011. After the 8th course, computed tomography revealed the disappearance of lymph node metastasis, except for 22mm of the mass located on the tail side of the antrum. MRI showed a low intensity mass on the T1 and T2-weighted images. FDG-PET did not show abnormal uptake in the tumor. EUS-FNA did not reveal a definitive diagnosis. We performed a laparotomy for diagnosis and treatment. Intraoperative findings showed that the tumor occurred in the mesentery of the transverse colon. The pathological diagnosis was angiomyolipoma. The patient has been free from recurrent disease for 2 years and 6 months. Angiomyolipoma originating in the transverse mesentery region is rare and, due to various percentage of tissue factors, there are no fixed view of image findings. Furthermore, a large tissue volume is need for histological diagnosis. Laparotomy is useful for diagnosis and therapy for angiomyolipoma occurring in the mesentery of the transverse colon.

Uncommon liver tumors: Case report and literature review

BACKGROUND

Beside hepatocellular carcinoma, metastasis, and cholangiocarcinoma, the imaging findings of other relatively uncommon hepatic lesions are less discussed in the literature. Imaging diagnosis of these lesions is a daily challenge. In this article, we review the imaging characteristics of these neoplasms.

METHODS

From January 2003 to December 2014, 4746 patients underwent liver biopsy or hepatic surgical resection in our hospital. We reviewed the pathological database retrospectively. Imaging of these lesions was reviewed.

RESULTS

Imaging findings of uncommon hepatic lesions vary. We discuss the typical imaging characteristics with literature review. Clinical and pathological correlations are also described. Primary hepatic lymphoma consists only of 1% of the extranodal non-Hodgkin lymphoma, and is defined as the one involving only the liver and perihepatic lymph nodes within 6 months after diagnosis. Combined hepatocellular and cholangiocarcinoma (cHCC-CC) shares some overlapping imaging characteristics with both HCC and cholangiocarcinoma because of being an admixture of them. Angiosarcoma is the most common hepatic mesenchymal tumor and is hypervascular in nature. Inflammatory pseudotumor is often heterogeneous on ultrasonography and with enhanced septations and rims in the portovenous phase after contrast medium. Angiomyolipoma (AML) typically presents with macroscopic fat components with low signal on fat-saturated magnetic resonance imaging (MRI) and presence of drainage vessels. Intraductal papillary neoplasm of the bile duct (IPNB) is thought of as a counterpart to the pancreatic intraductal papillary mucinous neoplasm. Most of the IPNBs secrete mucin and cause disproportional dilatation of the bile ducts. Mucinous cystic neoplasm (MCN) contains proteinaceous and colloidal components without ductal communication and characterizes with hyperintensity on T1-weighted imaging. Other extremely rare lesions, including epithelioid hemangioendothelioma and inflammatory pseudotumor-like follicular dendritic cell sarcoma, are also discussed. Hepatoblastoma and mesenchymal hamartoma, mostly in children, are also briefly reviewed as well.

CONCLUSION

It is important for radiologists to be familiar with the typical imaging features of the uncommon hepatic neoplasms. If imaging findings are not typical or diagnostic, further biopsy is required.

[Extrarenal Retroperitoneal Angiomyolipoma Masquerading as Retroperitoneal Liposarcoma : A Report of Two Cases]

We report two patients with extrarenal retroperitoneal angiomyolipoma masquerading as perinephric liposarcoma. Patient 1 : A 66-year-old man was diagnosed with a retroperitoneal tumor near the right renal hilum on an abdominal computed tomography (CT) performed before surgery for gastric cancer. A diagnosis of extrarenal retroperitoneal angiomyolipoma was made on the basis of negative uptake of fluorine- 18 2-deoxy-2-fluoro-D-glucose positron emission tomography (18F-FDG PET)/CT. However, because the tumor was found to have gradually enlarged at 18 months afterward, he underwent resection of the extrarenal fat tissue together with the right kidney. Patient 2 : A 56-year-old man underwent abdominal ultrasound during a periodic medical examination, which revealed a right retroperitoneal tumor. Because of the findings in the contrast-enhanced CT and positive uptake of 18F-FDG PET/CT, he underwent resection of the extrarenal fat tissue together with the right kidney. The pathological examination of the two tumors confirmed extrarenal angiomyolipoma. The differential diagnosis of extrarenal retroperitoneal angiomyolipoma from retroperitoneal liposarcoma is difficult even with the use of 18F-FDG PET/CT.

Differentiation of hepatocellular carcinoma from its various mimickers in liver magnetic resonance imaging: What are the tips when using hepatocyte-specific agents?

Hepatocellular carcinoma is the most common primary hepatic malignant tumor. With widespread use of liver imaging, various cirrhosis-related nodules are frequently detected in patients with chronic liver disease, while diverse hypervascular hepatic lesions are incidentally detected but undiagnosed on dynamic computed tomography and magnetic resonance imaging (MRI). However, use of hepatocyte-specific MR contrast agents with combined perfusion and hepatocyte-selective properties have improved diagnostic performance in detection and characterization of focal liver lesions. Meanwhile, the enhancement patterns observed during dynamic phases using hepatocyte-specific agents may be different from those observed during MRI using conventional extracellular fluid agents, leading to confusion in diagnosis. Therefore, we discuss useful tips for the differentiation of hepatocellular carcinoma from similar lesions in patients with and without chronic liver disease using liver MRI with hepatocyte-specific agents.

An Unusual Variant of Hepatic Inflammatory Angiomyolipoma: Report of a Rare Entity

Hepatic angiomyolipoma is a rare mesenchymal tumor with a broad spectrum of histological appearance. A 44-year-old female presented with abdominal discomfort. MRI revealed a 3.6 cm well-defined hepatic lesion. Ultrasound-guided core biopsy with imprint smears was performed. The smears showed histiocytes with a few epithelioid cells, mimicking an inflammatory lesion. The biopsy showed proliferation of epithelioid cells with aggregates of foamy histiocytes and scattered adipocyts, resembling hepatocellular neoplasm. The diagnosis of angiomyolipoma was clinched by the immunoprofile of the epithelioid cells, which were diffusely positive for HMB45, Mart-1 and focally positive for smooth muscle actin. To our best knowledge, this is the first reported case of biopsy diagnosed hepatic inflammatory angiomyolipoma with an unusual inflammatory infiltrate composed mainly of aggregates of foamy histiocytes.

[Renal angiomyolipoma with spontaneous retroperitoneal bleeding]

Angiomyolipoma (AML) is a benign tumour composed predominantly of blood vessels, smooth muscle tissue and adipose tissue. It is a rare disorder found in 0.1% of men and 0.22% of women. AML is most often manifested as a solitary tumour, but can also be found with multiple lesions in various organs. AML is predominantly asymptomatic, but may present with different symptoms depending on the size and position. Patients often have flank pain and microscopic or macroscopic haematuria. AML can also debut with spontaneous atraumatic bleeding in the retroperitoneum, Wunderlich's syndrome.