Lipomatous tumors of the liver: evaluation with CT and US

Liver Angiomyolipomas in Tuberous Sclerosis Complex-Their Incidence and Course

BACKGROUND

The purpose of this study was to evaluate the epidemiology and clinical significance of hepatic angiomyolipomas in patients with tuberous sclerosis complex.

METHODS

We performed a retrospective analysis of clinical and imaging data from 187 patients with tuberous sclerosis complex. The prevalence, progression, and potential relationship between liver lesions and other clinical findings, including genetic associations, were assessed.

RESULTS

Twenty-eight of 187 patients (14.9%) had hepatic lesions. There was a predominance of female over male patients in individuals with liver lesions (17 versus 11), with statistical significance in patients under five years of age (P < 0.05). All individuals having hepatic lesions who also had available genetic testing data (n = 20) were diagnosed with a TSC2 gene mutation. All patients with liver lesions had coexisting renal angiomyolipomas (AMLs) (P < 0.05). The age of onset of renal lesions was lower and their prevalence was significantly higher in patients with liver involvement (P < 0.05). In most instances, hepatic lesions measured several millimeters in diameter and were clinically asymptomatic. Progressive lesion growth was documented in six individuals but with no clinical consequences to date.

CONCLUSIONS

This study confirms the association of hepatic lesions with TSC2 mutations, a common origin of liver and renal AMLs, as well as the predominance of female patients in this group. Hepatic AMLs are relatively common but mostly benign lesions.

Synchronous occurrence of a hepatic myelolipoma and two hepatocellular carcinomas

Myelolipoma is a rare tumor composed of fat and bone marrow components, most of which are located in the adrenal gland. Myelolipoma in the liver is extremely rare. To date, only 10 cases have been reported in the English-language medical literature. In one of these cases, the hepatic myelolipoma was found within a hepatocellular carcinoma (HCC). In the present study, we report the first case of the synchronous occurrence of hepatic myelolipoma and HCCs in different liver sections of one patient, a 26-year-old female who was admitted to our hospital because of a 4-d history of upper abdominal pain. The unenhanced computed tomography (CT) images showed a well-defined low-density mass with adipose components in the right liver lobe, 4.2 cm × 4.1 cm in size. Two inhomogeneous low-density masses were found in the left liver lobe, 8.6 cm × 7.7 cm and 2.6 cm × 2.6 cm in size. The masses in both the right and left liver lobes were heterogeneously enhanced in the contrast-enhanced CT images. Based on the results of the imaging examination, the mass in the right liver lobe was preliminarily considered to be a hamartoma, and the two masses in the left liver were preliminarily considered to be HCCs. We performed a right hepatectomy, a left hepatic lobectomy, and a cholecystectomy. Microscopic and immunohistochemical results revealed that the tumor in the right liver lobe was a hepatic myelolipoma, and that the two tumors in the left liver lobe were HCCs.

Angiomyolipoma of the Liver

Angiomyolipoma, a rare benign liver tumor, was observed in a 50-year-old woman examined with US, CT, MR imaging and angiography. Dynamic studies using CT and MR imaging were valuable in differentiating the disease from hepatocellular carcinoma with fat deposits.

Quantitative analysis of hepatic fat fraction by single-breath-holding MR spectroscopy with T₂ correction: phantom and clinical study with histologic assessment

The focus of this study was on the investigation of the accuracy of the fat fraction of the liver by use of single-breath-holding magnetic resonance spectroscopy (MRS) with T (2) correction. Single-voxel proton MRS was performed with several TE values, and the fat fraction was determined with and without T (2) correction. MRS was also performed with use of the point-resolved spectroscopy sequence in single breath holding. The T (2) values of both water and fat were determined separately at the same time, and the effect of T (2) on the fat fraction was corrected. In addition, MRS-based fat fractions were compared with the degree of hepatic steatosis (HS) by liver biopsy in human subjects. With T (2) correction, the MRI-derived fat fractions were in good agreement with the fat fractions in all phantoms, but the fat fractions were overestimated without T (2) correction. R (2) values were in good agreement with the preset iron concentrations in the phantoms. The MRI-derived fat fraction was well correlated with the degree of HS. Iron deposited in the liver affects the signal strength when proton MRS is used for detection of the fat signal in the liver. However, the fat signal can be evaluated more accurately when the T (2) correction is applied. Breath-holding MRS minimizes the respiratory motion, and it can be more accurate in the quantification of the hepatic fat fraction.

Fat-containing nodules in the cirrhotic liver: chemical shift MRI features and clinical implications

OBJECTIVE

The purpose of this study was to determine the ability of MRI to predict malignancy in fat-containing nodules in the cirrhotic liver.

MATERIALS AND METHODS

In 38 patients with cirrhotic livers, focal lesions > or = 5 mm containing fatty components were identified on chemical shift gradient-echo MRI. Positive predictive values (PPVs) for benignity and malignancy were calculated on the basis of lesion size, T1-weighted hypointensity, T2-weighted hyperintensity, and arterial hypervascularity on the initial MR images. The number of the fatty nodules (group A, up to 4; group B, numerous) in individual patients was also correlated with the malignant potential of the lesions that were verified pathologically or by follow-up imaging studies.

RESULTS

In 31 group A patients, 21 (47%) of the 45 lesions showed a malignant course, and their mean diameter (18.8 mm) was larger (p = 0.007) than that (10.5 mm) of benign lesions. In seven group B patients, all 35 lesions (the five largest lesions in each patient; mean diameter, 7.8 mm) proved to be benign. The PPV of larger (> or = 15 mm) fat-containing nodules for malignancy was 85% (11/13 lesions). Six (55%) of 11 immediately diagnosed hepatocellular carcinomas were entirely hypointense on unenhanced in-phase T1-weighted images. The PPV of T2-weighted hyperintensity and arterial hypervascularity for the diagnosis of malignancy was 100% in group A patients.

CONCLUSION

In the cirrhotic liver, large size (> or = 15 mm) and T1-weighted hypointensity on in-phase images strongly suggest malignancy of the fat-containing nodules. The presence of numerous nodules < 1 cm suggests that the lesions are benign.

Frequency and imaging appearance of hepatic angiomyolipomas in pediatric and adult patients with tuberous sclerosis

OBJECTIVE

This study evaluates the frequency and imaging appearance of hepatic angiomyolipomas in pediatric and adult patients with tuberous sclerosis.

CONCLUSION

Multiple hepatic angiomyolipomas are often found in patients with tuberous sclerosis, particularly in those with bilateral diffuse renal angiomyolipomas.

Hepatic angiomyolipoma: various appearances on two-phase contrast scanning of spiral CT

The purpose of this study was to describe and analyze the various appearances of hepatic angiomyolipoma (AML) on the two-phase contrast scans of spiral CT and find out the valuable signs suggesting the diagnosis. Spiral CT scanning of pre- and post-contrast arterial phase, portal venous phase were performed in 12 cases. We found that 11 of 12 lesions appeared as hypodense, the other one appeared as slightly hyperdense on pre-contrast CT scans. On the arterial phase, 11 lesions were markedly enhanced, with the central vasculature opacification in eight lesions; the only other lesion showed no marked enhancement, but with massive vessels seen within the lesion. On the portal venous phase, eight lesions remained in enhancement with the central vessels also seen in six lesions. Our results revealed that two-phase contrast scanning could demonstrate some characteristic features of AML, such as fat components within the lesions, hypervascular tumors, the absence of capsule. Especially the central vessels within the lesions suggested strongly the diagnosis of AML. As for atypical cases, the diagnosis remained difficult and should be differentiated from other hypervascular lesions by means of other imaging modalities or needle puncture biopsy.

Lymphangiectasia within angiomyolipoma in a tuberous sclerosis patient

This is a presentation of a case of tuberous sclerosis with multifocal hamartomas in the retroperitoneum, both kidneys, and the liver. Lymphangiectasia and numerous ectatic lymphatic channels penetrating through the retroperitoneal angiomyolipoma were demonstrated by lymphography and computed tomography. The findings in our study may document the presence of degenerative change in the lymphatic system--not just in elastic vessels--an association which has not yet been reported in the radiological literature.

CT and MR imaging of benign hepatic and biliary tumors

Benign hepatic and biliary tumors can present a difficult diagnostic challenge. Spiral computed tomography (CT) and magnetic resonance (MR) imaging are useful in the detection and characterization of these tumors. Imaging characteristics of lesions such as hepatic cyst, hemangioma, focal nodular hyperplasia (FNH), and hepatic adenoma are well known. Hepatic cysts demonstrate water attenuation at CT, are isointense relative to water at MR imaging, and do not enhance after intravenous administration of contrast material. Hemangiomas demonstrate characteristic nodular peripheral enhancement on early-phase images with subsequent fill-in centrally at both modalities. FNH classically demonstrates intense early enhancement with washout on delayed images. Although hepatic adenoma can also demonstrate intense early enhancement, it has a tendency to bleed and thus often appears more heterogeneous than FNH due to hemorrhage. Benign hepatic tumors that are less well described in the imaging literature include hepatic lipoma or angiomyolipoma, infantile hemangioendothelioma, and mesenchymal hamartoma. Hepatic lipoma has fat attenuation at CT, is isointense relative to fat at MR imaging, and does not enhance after intravenous administration of contrast material. Hepatic angiomyolipomas contain a variable amount of soft tissue in addition to fat and may therefore demonstrate enhancement at both modalities. The CT and MR imaging appearances of infantile hemangioma are similar to those of adult hemangioma. Infantile hemangioendothelioma occurs in infants under 6 months of age and is typically a larger lesion. Mesenchymal hamartoma also occurs in children, and its imaging appearance depends on the presence of stromal elements and the protein content of the cyst fluid. Familiarity with these imaging features can help distinguish particular disease entities.

Hepatic angiomyolipoma: a clinicopathologic study of 30 cases and delineation of unusual morphologic variants

Hepatic angiomyolipoma (AML) is frequently misdiagnosed. HMB-45 is a promising immunomarker for this tumor that leads to recognition of some AMLs with unusual morphology. The purpose of this collaborative study is to better define the morphologic variations of AML. Thirty AMLs were examined, including four biopsy specimens and two fine-needle aspirates. The diagnosis was confirmed by the presence of HMB-45-positive myoid cells. Almost half the cases were originally misdiagnosed as carcinomas or sarcomas. There was marked female predominance (25:5), and the mean age was 48.7 years (range 29-68). Three patients (10%) had evidence of tuberous sclerosis and all had renal AML. According to the line of differentiation and predominance of tissue components, the tumors was subcategorized into mixed, lipomatous (> or = 70% fat), myomatous (< or = 10% fat), and angiomatous type. The mixed type was the most common (11 resected cases), comprising sheets of epithelioid muscle cells admixed with islands of adipocytes, abnormal vessels, and frequently, hematopoietic cells. Six tumors (including three from biopsy specimens) were heavily fatty and showed predominantly adipocytes with epithelioid and short spindle myoid cells webbed between fat cells. Of 10 myomatous AMLs, five tumors showed a pure sinusoidal trabecular pattern and comprised mainly epithelioid cells. Typically, mature adipocytes were absent or scanty, but fat was seen as fine droplets within cytoplasm or as occasional large globules in sinusoids. Pelioid and inflammatory pseudotumor-like patterns were identified focally. Regarding cellular features of the myoid cells, most of the epithelioid cells were either eosinophilic or clear with spiderweb cell morphology. Three AMLs showed an almost purely oncocytic appearance with scanty fat. Large pleomorphic epithelioid cells existed as small foci. Spindle cells arranged in long fascicles were uncommon. D-PAS-positive globules were common around pelioid areas. Brown pigments with staining characteristics of hemosiderin and/or melanin were noted. In conclusion, we propose HMB-45-positive myoid cells as the defining criterion of hepatic AML, which is a tumor capable of dual myomatous and lipomatous differentiation and melanogenesis. Because of its protean morphologic appearance, recognition of the various variant patterns and cell types is important for a correct diagnosis, assisted by immunohistochemical confirmation with HMB-45. Trabecular and oncocytic cell tumors appear to stand out as distinctive subtypes.

Benign lesions of the liver

Although many hepatic lesions can overlap significantly in their imaging appearance, an imaging approach that is based upon identifying the pathologic and functional components of a lesion can aid in distinction from other entities. In this manner, the diagnostic evaluation can be tailored using the appropriate imaging modality for the lesion at hand. An understanding of the benign liver lesions based on the cellular line of origin and subsequent functional components aids in grasping their expected imaging appearance and may aid in their distinction from malignant tumors. Thus, an imaging approach leading to diagnosis of these tumors should be based on this underlying knowledge of the functional components and cells within the lesion to be studied. For lesions with Kupffer's cell activity, such as FNA, Tc-99m sulfur colloid scan or MR imaging with SPIO may yield the most diagnostic information. For lesions such as hepatic cysts or angiomyolipoma, the diagnosis is usually not a dilemma. For hemangiomas, the most commonly encountered benign hepatic lesion, distinction from other entities may be readily apparent from the initial CT scan or US examination, or it may require additional evaluation with MR imaging. Finally, for other lesions with many cellular components, such as HCA, the imaging findings may not be specific enough by any modality to preclude tissue diagnosis. In any case, it is important to know the diagnostic accuracy and limitations of the imaging modalities available for assessment of any given benign hepatic mass.

Comparison of in-phase and opposed-phase GRE and conventional SE MR pulse sequences in T1-weighted imaging of liver lesions

PURPOSE

Our goal was to compare in-phase (IP) and opposed-phase (OP) GRE and conventional SE sequences in T1-weighted (T1-W) imaging of the liver and to evaluate chemical shift GRE imaging in characterizing liver/lesions for fat content.

METHOD

IP and OP T1-W GRE with fast low angle shot (FLASH) technique and T1-W SE sequences were compared in 162 patients at 1.0 T. Chemical shift GRE imaging was used to characterize lesions with fat content. Two hundred sixteen lesions were analyzed in three groups of liver: (a) "normal" liver (n = 74 with 110 lesions); (b) cirrhotic liver (n = 76 with 85 lesions); and (c) fatty liver (n = 12 with 21 lesions). Liver/lesion contrast and liver/lesion contrast-to-noise ratio were assessed for lesion detectability. The percentage of signal intensity variation (SIV) between IP and OP images was used to characterize lesions for fat content.

RESULTS

The OP GRE sequence had significantly higher contrast for normal and cirrhotic livers (p < 0.001), and the IP GRE sequence had significantly higher contrast and contrast-to-noise ratio for fatty liver (p < 0.001). There were no significant differences between OP, IP, and T1-W SE imaging in cirrhotic cases for contrast-to-noise ratio (p < 0.28). Chemical shift imaging detected fat in 21 lesions (9.7%, mean SIV, 191.1%) (sensitivity and specificity 100% when compared with fine needle aspiration cytology).

CONCLUSION

OP GRE sequences could replace conventional SE sequences in T1-W imaging in nonfatty livers, whereas in fatty livers, T1-W SE sequences could be obviated, but both OP and IP sequences are necessary. Chemical shift imaging (OP and IP) can be used to accurately characterize lesions for fat content.

Hepatic angiomyo(myelo)lipoma: difficulties in radiological diagnosis and interest of fine needle aspiration biopsy

We report the case of a patient admitted for acute heart failure associated with severe dilated cardiomyopathy in whom a large hepatic tumor of the right lobe of the liver was incidentally discovered. A fine needle biopsy was performed that led to the diagnosis of angiomyo(myelo)-lipoma (AMML). The difficulties in radiological diagnosis of these very rare heterogeneous benign tumors of the liver and the interest of fine needle aspiration biopsy are discussed.

Hepatic angiomyolipoma developing during the follow-up of ulcerative colitis: report of a case and review of the literature

Hepatic angiomyolipoma is a rare tumor composed of spindle-shaped and epithelioid smooth muscle cells, adipose tissue, and proliferating blood vessels. We report the first documented case of this tumor developing in a patient with ulcerative colitis. A solitary tumor (7.5 x 7.5 x 7 cm) was detected in the left lateral segment of the liver and a left hepatic lobectomy was performed. The diagnosis of angiomyolipoma was confirmed by a pathological examination. We also review the literature on previously reported cases of hepatic angiomyolipoma.

Multifocal angiomyolipoma in a patient with tuberous sclerosis

Angiomyolipomas are rare lesions that occur most commonly in the kidney, but also can occur in the liver and rarely, in the lymph nodes. Its rare association with tuberous sclerosis has been suggested, but never proved. We report a patient with multiple visceral angiomyolipomas as well as visceral vessel aneurysms and tuberous sclerosis. The association of the three lesions suggests a possible common connective-tissue defect.

Hepatic angiomyelolipoma and tuberous sclerosis

A patient with angiomyelolipoma of the liver, together with radiological evidence of pancreatic, renal and bony lesions characteristic of tuberous sclerosis, is described. Although the patient had no other clinical features of tuberous sclerosis, her daughter was found to suffer from the classical triad of this syndrome and also has had hepatic lipomatous lesions and bony involvement. This is the first histologically proven case of hepatic angiomyelolipoma associated with tuberous sclerosis.

Case report: diffuse fatty infiltration of the renal parenchyma secondary to bilateral angiomyolipomas--features on ultrasound and computed tomography

A case is described where ultrasound demonstrated diffusely increased echogenicity in massively enlarged kidneys. Computed tomography confirmed fatty replacement of the renal parenchyma, allowing a confident diagnosis of multiple bilateral angiomyolipomas in a clinical setting of tuberous sclerosis. This is the first ultrasound demonstration of such diffusely echogenic kidneys in angiomyolipoma.

Focal fatty change of the liver: cytologic findings in a radiographic mimic of metastases

Fine-needle aspiration (FNA) is being increasingly utilized for the workup of patients with suspected metastatic disease. In the course of these biopsies, cytologists are being confronted by a variety of nonneoplastic lesions which radiographically simulate metastatic deposits. Some of these lesions will predominately reveal hepatocytes. One of these cytologically poorly characterized lesions is focal fatty change. Aspirates show a population of benign hepatocytes with single or multiple clear cytoplasmic vacuoles. Recognition of the entity along with accurate needle placement in the nodule can establish the diagnosis of focal fatty infiltration and negate the need for further biopsies.

Multiple hepatorenal angiomyolipomas: diagnosis with fat suppression, gadolinium-enhanced MRI

Hepatic angiomyolipoma is a rare tumor which may occur as a solitary mass or as an associated finding with tuberous sclerosis. While computed tomography allows identification of the fat component of the lesion, magnetic resonance imaging (MRI) can provide similar information, as well as multiplanar visualization and further characterization of the vascular component of the lesion. MRI utilizing fat suppression and gadolinium enhancement may best provide all of the above information, as is demonstrated in this case report, thus potentially representing the imaging modality of choice.

Hepatic angiomyolipoma

The imaging and pathological appearances of a hepatic angiomyolipoma are presented. On ultrasound (US), the mass was well-defined and echogenic. On computed tomography (CT), the lesion appeared of soft tissue density with peripheral foci of lower density. The case illustrates the difficulty of detecting the fatty content of a tumor by CT when the fatty content represents only a small portion of the lesion. Fine-needle aspiration (FNA) cytology and needle biopsy did not yield diagnostic material, and the tumor was resected.

Liver angiomyolipoma: classic and unusual presentations

Two cases of liver angiomyolipoma (AML) are presented. The first case has the classical imaging findings previously reported. The second case has no fat content on the various imaging modalities. AML should probably be included in the differential diagnosis of any hypervascular lesion of the liver. Preoperative diagnosis with core biopsy is possible.

Angiomyolipomas of the liver in tuberous sclerosis

Although the association of tuberous sclerosis and renal angiomyolipomas is well established, the occurrence of hepatic hamartomatous lesions in this disease is less well documented. We describe two cases of tuberous sclerosis with associated multiple intrahepatic angiomyolipomas, and we review the literature on this subject. Radiologically, angiomyolipomas can range from entirely lipomatous to completely solid, features which are present in our cases. A characteristic finding of the hepatic involvement in this disease appears to be the multiplicity of the lesions. We suggest that in the setting of tuberous sclerosis it is reasonable to assume that intrahepatic lesions represent angiomyolipomas. However, in nontuberous sclerosis patients with similar findings malignancy cannot be excluded.

Preoperative diagnosis of angiomyolipoma of the liver

We experienced a case of surgically proven hepatic angiomyolipoma, a rare primary benign lipomatous tumor, which was preoperatively diagnosed by defining of its characteristic histologic components and benign radiologic nature with various imaging modalities. It was the first case that full radiologic evaluation was taken and internal vascular proliferation was defined by using dynamic bolus computed tomography (CT) prior to angiography.

Worsening right flank pain over a 24-hr period

AML is a benign renal tumor composed of variable quantities of mature vascular, smooth muscle and fatty elements. They occur as an isolated finding, classically in middle-aged females, or in association with tuberous sclerosis. When symptomatic, they typically present with flank pain secondary to hemorrhage. CT is the diagnostic imaging modality of choice. The diagnosis can usually be made based on the recognition of fat within the lesion. When discovered, asymptomatic lesions are generally monitored by follow-up imaging studies, and if they remain stable, no intervention is required. Arterial embolization has become the recommended treatment of choice in some instances, particularly in cases with associated hemorrhage.

Hepatic angiomyolipoma pre-operatively diagnosed by imaging

An asymptomatic patient with pre-operatively diagnosed solitary angiomyolipoma is reported. The tumour was a well defined, fat density mass on computerized tomography (CT) and magnetic resonance imaging (MRI), and a hyperechoic nodule with a sharp margin on ultrasonography (US). The lesion was hypervascular on arteriography and CT during hepatic angiography. Chemical shift MRI confirmed the fat component within the lesion. Although a review of the literature shows this tumour to be rare and difficult to differentiate from a malignant lesion pre-operatively, the pre-operative diagnosis of angiomyolipoma is considered feasible when the characteristic findings as described here are present.

Liver hamartomas in tuberous sclerosis

Three patients with tuberous sclerosis (TS) and hepatic hamartomas are presented. Liver lesions are uncommonly documented in TS, compared to renal angiomyolipomas. The imaging characteristics of liver hamartoma in TS may resemble those of renal angiomyolipoma, hepatic cavernous haemangiomas, metastasis or abscess.

Hepatic angiomyolipomas with a deceptive trabecular pattern and HMB-45 reactivity

We report two cases of giant hepatic angiomyolipoma with a prominent component of epithelioid smooth muscle cells exhibiting a distinctive trabecular arrangement. These cells possessed peripherally vacuolated and centrally condensed hyaline cytoplasm. The nuclei were eccentrically placed in the cytoplasm. Immunohistochemically, they expressed HMB-45 intensely in the central condensed cytoplasm and actin in a perimembranous fashion. Staining for desmin, myoglobin and vimentin was negative. HMB-45 may prove to be a sensitive marker for angiomyolipoma with epithelioid cells. Hepatocellular carcinoma and other hepatic tumours with polygonal clear cells can be readily distinguished by these means.

MR imaging of hepatocellular carcinoma at 1.5 Tesla

The authors investigated the magnetic resonance appearance of hepatocellular carcinoma using a 1.5-Tesla magnet. Twenty-four patients with pathologically proven hepatocellular carcinoma had magnetic resonance imaging (MRI) studies, which were retrospectively reviewed. All patients were imaged with at least two of the following techniques: (1) T1-weighted (T1W), (2) T1-weighted with Gd-DTPA enhancement (T1W-E), (3) T2-weighted (T2W), (4) proton density (PD), and (5) gradient-recalled echoes (GRE). T1W images were equal to T2W images for tumor detection using a grading system. T1W images were slightly better than T2W images for the total number of lesions detected. The other pulsing techniques (PD, T1W-E, and GRE) detected fewer lesions. Eight cases of hepatocellular carcinoma (33%) had nonhomogeneous increased signal intensity on both T1W and T2W images. The authors conclude that T1W images are equal to T2W images for detection of hepatocellular carcinoma. The authors also conclude that 33% of hepatocellular carcinomas have an imaging pattern with increased signal intensity on both T1W and T2W images. This pattern is atypical for most other hepatic masses and hence can be used to suggest the mass is hepatocellular carcinoma.

Incidence of hepatic hamartomas in tuberous sclerosis

Hepatic hamartomas were thought to be a rare finding in patients with tuberous sclerosis. The purpose of this study was to assess their incidence in children with tuberous sclerosis and to review the literature. During 1984-90 we examined 51 children by ultrasonography; there were 25 boys and 26 girls. Their age ranged from 3 months to 18 years. Liver hamartomas were seen in 12 (23.5%) of the children, more often in girls than boys (5:1). Their incidence increased with age reaching 45% in children over the age of 10. They did not produce any symptoms of hepatic dysfunction. Our study and review of reported cases prove that hepatic hamartomas are a common finding in patients with tuberous sclerosis and may be very helpful in providing a more accurate diagnosis and consequently help in genetic counselling.

Case report: lipoma of the liver--ultrasound, CT and MR imaging

A case of lipoma of the liver is presented; ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI) findings are reviewed and compared with previous reports. The ultrasound pattern and appearance of the tumour in CT as well as MRI are discussed.

Hepatic angiomyolipoma with striated granules and positivity with melanoma--specific antibody (HMB-45): a report of two cases

Angiomyolipoma occurs rarely in the liver, with only 25 previous cases being reported in the English literature. The article describes two additional cases, one of which was multicentric, with results of ultrastructural and immunocytochemical studies. Many of the tumor cells contained numerous electron-dense granules, some with transverse striations like those found in melanosomes. Both tumors stained positively for S-100 protein and melanoma-specific antibody HMB-45. One case also expressed vimentin and neuron-specific enolase. Both were negative for cytokeratin, carcinoembryonic antigen, alpha-fetoprotein, desmin, muscle-specific actin, factor VIII antigen, and chromogranin. Comparison of our ultrastructural findings with those of classic renal angiomyolipoma raises the possibility that the melanosomelike structures may represent renin granules rather than melanosomes, although the latter are not excluded. Expression of HMB-45 in angiomyolipoma has important biologic and diagnostic implications, whether or not it reflects melanocytic differentiation.

Perirenal lipoma versus renal cell carcinoma

Pure renal and perirenal lipomas are rare. They arise from renal cortex, capsule, or perirenal tissue, and may be difficult to distinguish from renal adenocarcinomas. We report on a patient who presented with a renal mass that had the radiologic findings suggestive of a renal cell carcinoma, but proved to be a simple lipoma.

Focal fatty change of the liver. A review and a case associated with continuous ambulatory peritoneal dialysis

Focal fatty change (FFC) of a liver with unequivocal normal architecture is rare. A review of the literature revealed 39 histologically well-documented cases. Well-known steatogenic conditions were present in most of these cases. Focal ischaemia or a varying rate of mobilization of fat in the liver have been suggested as a cause of the focality of the lesions. FFC occurring in a diabetic patient on continuous ambulatory peritoneal dialysis (CAPD) is presented. The FFC in this and in ten previously reported cases associated with CAPD and intraperitoneal insulin therapy had a unique subcapsular distribution, which may suggest a specific pathogenetic mechanism involving insulin. The clinical significance of FFC in the differential diagnosis from other fatty lesions of the liver is summarized.

Angiomyolipoma of the liver: immunohistochemical study of a case

Angiomyolipoma, a not uncommon tumor of the kidney, is rarely encountered in the liver. We report a case of angiomyolipoma of the liver in a 68-year-old woman, in which immunohistochemical study was performed.

Angiomyolipoma of the liver

Hepatic angiomyolipoma is a rare tumour of the liver. Its behaviour is benign and this paper reports the first case described in Australia. A review of the literature suggests that the use of ultrasonography, computerized tomography and angiography should enable pre-operative diagnosis to be made with relative certainty, yet the difficulties with histological diagnosis, particularly on needle biopsy, may necessitate resection.

Lipoma of the liver: US, CT, and MRI appearance

A case of hepatic lipoma is reported. Since the sonographic (US), computed tomographic (CT), and magnetic resonance imaging (MRI) findings are characteristic, we believe more aggressive diagnostic procedures are not necessary.

An electron microscopic study of hepatic angiomyolipoma

Three cases of hepatic angiomyolipoma, each composed of an intimate mixture of numerous abnormal blood vessels and various-sized fat, spindle and/or epithelioid cells, are presented along with the findings of an electron microscopic study. The spindle cells were confirmed to be smooth muscle by immunohistochemical staining for desmin and by their ultrastructural characteristics. The mature fat cells, smooth muscle cells, immature short spindle cells apparently intermediate or transitional between the former two cell types, and the epithelioid cells were observed adjacent to the endothelial cells. Ultrastructurally, the epithelioid cells were characterized by unusual cytoplasmic organelles such as myofilaments having focal densities and dense attachments, numerous large electron-dense bodies, and a large number of glycogen particles and lipid droplets. Therefore, it is considered that the immature short spindle and epithelioid cells in hepatic angiomyolipoma might be primitive mesenchymal cells having an ability to differentiate toward both smooth muscle and fat cells.

Benign liver tumors

This article discusses the most important benign liver tumors, both in adult and pediatric patients. A pathologic discussion of each neoplasm is included to provide a basis for understanding the radiologic-pathologic correlation that is used throughout the monograph. The benign liver tumors are presented according to their frequency. Therefore, hemangioma, the most common primary benign liver neoplasm, is discussed first, followed by focal nodular hyperplasia, hepatocellular adenoma, and the benign primary pediatric tumors--infantile hemangioendothelioma and mesenchymal hamartoma. Finally, a brief discussion of nodular regenerative hyperplasia and other rare hepatic masses is included. Bile duct cyst (simple, non-parasitic cyst of the liver) is not included since it is not a neoplasm. Likewise, cystadenoma is not discussed since it originates from the biliary duct cell and is appropriately included in the biliary neoplasms category.

CT demonstration of extension of renal angiomyolipoma into the inferior vena cava in a patient with tuberous sclerosis

The authors present a case of tumor thrombus in the inferior vena cava produced by angiomyolipoma in a young woman with tuberous sclerosis. Diagnosis was made by computed tomography (CT) by measuring the attenuation values of the tumor thrombus. The values obtained were characteristic of fat, demonstrating that tumoral invasion was the cause of the thrombus. To our knowledge, this is the first description of such an association shown by CT in the literature.

Giant hepatic angiomyolipoma simulating focal nodular hyperplasia

A case of hepatic angiomyolipoma occurring in a 41-year-old woman, the eighteenth case in literature, is reported herein. The radiographic imagings of the tumor simulated those of focal nodular hyperplasia; namely, the tumor was hyperechoic on ultrasound, hypodense on computed tomography, hypervascular on angiography, and exhibited an uptake of technetium (Tc)-99m phytate. The diagnosis was established after successful removal of the huge tumor from the right hepatic lobe. Histologically, the tumor was angiomyolipoma which was made up of three components, blood vessels, smooth muscle and fatty tissue. Furthermore, extramedullary hematopoiesis, which is usually seen in this tumor was confirmed. The differentiation of hepatic angiomyolipoma from FNH is also discussed.

Hepatic lipomas: ultrasound and computed tomographic findings

Five cases of solitary hepatic lipoma are described. These rare tumors have ultrasound (US) and computed tomographic (CT) characteristics that suggest the diagnosis. As imaged by US, hepatic lipomas always correspond to a highly echogenic, well-limited lesion with posterior attenuation. Precontrast CT scans reveal a low-density lesion (-20 to -70 HU); following contrast material injection, the tumor density may either remain negative (pure hepatic lipoma) or become positive (limit, 40 HU) when there is an associated adenomatous component. Hepatic lipomas involve no risk of degeneration, and follow-up by US is sufficient. A case of lipoma of the falciform ligament and a case of a hepatic pseudolipoma are also described; sonograms were negative in both instances, and CT was required for diagnosis.