CT demonstration of fat tissue in malignant renal neoplasms: atypical Wilms' tumors

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.

CT Demonstration of Fat Density in Renal Cell Carcinoma

The presence of fat in a renal mass is almost pathognomonic of angiomyolipoma. We report a rare instance of CT demonstration of foci of fat density in a renal cell carcinoma.

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 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.

Giant renal angiomyolipoma with fatal hemorrhage due to a large pseudoaneurysm

We report a case of giant renal angiomyolipoma (AML) with a large pseudoaneurysm causing fatal hemorrhage. A 60-year-old woman presented with right-sided abdominal pain. Sonographic examination revealed a large hyperechoic renal mass. CT examination of the abdomen revealed a 15-cm AML of the right kidney with a large hemorrhagic area within it. Subsequent color Doppler examination revealed a 2.9-cm pseudoaneurysm arising from the upper segmental branch of the right renal artery. The patient, who was about to undergo transcatheter embolization of the pseudoaneurysm, died from cardio-respiratory arrest. The autopsy findings confirmed a large right renal AML containing a thrombosed pseudoaneurysm and a large perinephric hematoma.

Hyperattenuating renal masses: etiologies, pathogenesis, and imaging evaluation

Some renal masses have higher attenuation than the surrounding renal parenchyma at computed tomography (CT). Their hyperattenuation is usually the result of proteinaceous fluid or densely packed cells. Most hyperattenuating renal masses are benign hemorrhagic or proteinaceous cysts. However, solid enhancing hyperattenuating renal masses may have malignant as well as benign causes. Possible malignant causes include renal cell carcinoma and lymphoma; benign causes include angiomyolipoma with minimal fat. It is important to identify the cause of a hyperattenuating renal mass so as to avoid unnecessary surgical resection or ablation. CT may be useful for diagnosing benign hyperattenuating renal cysts, hematomas, and vascular anomalies that appear masslike. However, some solid, enhancing, hyperattenuating masses cannot be diagnosed confidently with CT alone: Small (< or = 3-cm-diameter), homogeneously enhancing, hyperattenuating renal masses depicted on CT images may be either benign angiomyolipomas with minimal fat or renal cell carcinomas. Magnetic resonance (MR) imaging may be helpful for differentiating between angiomyolipomas with minimal fat and clear cell renal cell carcinomas; however, differentiation between angiomyolipomas with minimal fat and papillary renal cell carcinomas often is not possible on the basis of MR imaging. In such cases, a percutaneous biopsy may be useful for diagnosis. If the results of MR imaging and percutaneous biopsy are not definitive, surgery is warranted.

Imaging of renal tumours in infancy and childhood

There is a large range of benign and malignant renal neoplasms. This article lists the most benign, indeterminate and malignant renal tumours that occur during infancy and childhood. It briefly describes the most important entities, including their imaging features, and important complications. Differential diagnosis and pitfalls are discussed, and a brief suggestion for a standardised imaging algorithm is proposed. Although modern imaging techniques, including colour Doppler sonography, helical or multidetector CT, and MR have significantly improved imaging potential, the definite diagnosis on tumour entity still is established only by histology.

Fatty Metastatic Lesions in 2 Patients with Renal Clear-Cell Carcinoma

This is a case report of 2 patients with previously resected renal cell carcinoma who present with unusual fatty lesions that proved to be metastases.

Low attenuation intratumoral matrix: CT and pathologic correlation

Diffuse low attenuation lesions on CT scans are caused by various pathologic conditions, especially differences of the intratumoral matrix. Low attenuation on CT scans was more defined than fat density and less than muscle density, the so-called near water density. We present representative cases of low attenuation lesions in correlation with their pathologic features. Intratumoral matrix showing diffuse low attenuation on CT was classified into eight groups: fatty degeneration/fatty metamorphosis, intracellular high lipid content, large amounts of lipid-laden macrophages, mucin-producing tumor, myxoid degeneration/myxoid matriX, massive necrosis, true cystic growth of the neoplasm, and massive edema. Lesions with fatty degeneration or intracellular high lipid content could be shown as negative CT attenuation. Knowledge of the neoplasms or disease processes that tend to have such pathology will lead to correct interpretation of CT scans of various organs.

CT demonstration of liquid intratumoral fat layering in a necrotic renal cell carcinoma

We describe a case of clear-cell adenocarcinoma of the kidney with CT evidence of fat that contradicts the rule that radiologically demonstrable fat is absent in renal carcinoma. The cyst-like appearance, egg-shell parietal calcifications, and extrarenal development of the mass suggested a preoperatively incorrect diagnosis of teratoma.

Outcome analysis of 42 cases of renal angiomyolipoma

Angiomyolipomas were found in 42 kidneys in 23 female and 8 male patients at our medical center. Angiomyolipoma was diagnosed by computerized tomography (CT) alone in 55% of the cases, and by a combination of ultrasound and CT in 36%. Nine of 11 patients with bilateral angiomyolipoma had associated tuberous sclerosis. Treatment consisted of observation in 22 patients, selective arterial embolization in 6, partial nephrectomy in 6 and nephrectomy in 8. A total of 17 patients who were observed had tumors smaller than 4 cm. and 4 h had angiomyolipoma of 4 to 10 cm. With a mean followup of 3.8 years, no observation patient had subsequent renal hemorrhage and only 1 (tumor larger than 10 cm.) had radiographic progression. Despite progression, the latter patient remained asymptomatic for 18 years. Selective arterial embolization (3 tumors 4 to 10 cm. and 3 larger than 10 cm.) resulted in preservation of renal function at a mean of 1 year. All patients treated with partial nephrectomy (6 tumors 4 to 10 cm.) maintained stable renal function without recurrence during a mean 4.7-year followup. Similarly, all individuals who underwent nephrectomy (4 tumors smaller than 4 cm., 3 tumors 4 to 10 cm. and 1 tumor larger than 10 cm.) have stable renal function. We recommend renal conservation for patients with renal angiomyolipoma using a strategy of observation for small asymptomatic tumors, partial nephrectomy for moderate size tumors and selective arterial embolization of large tumors not amenable to partial nephrectomy.

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.

Fat containing renal mass in childhood: a case report of teratoid Wilms tumor

Renal masses in childhood rarely contain adipose tissue as a major component. We report a case of teratoid Wilms tumor, an atypical variant of nephroblastoma, in which bilateral renal masses were found on computerized tomography to have a high fat content. Previously reported cases have had clinical characteristics in common with our case. However, our patient died of metastatic disease, which to our knowledge has not been previously described.

CT appearance of giant renal angiomyolipoma

Renal angiomyolipomas are rare benign tumors readily identified by computed tomography due to their high fat content. When they attain giant proportions other fatty neoplasms, specifically liposarcomas, cannot be excluded based on the radiographic findings. A case in which a notch defect in the lateral border of the kidney was the single most important clue as to the intrarenal origin of the mass and led to the correct pre-operative diagnosis is presented.

Adrenal myelolipoma: clinical, radiologic, and histologic features

The adrenal myelolipoma is a benign, endocrinologically inactive tumor whose histologic structure consists of mature adipose tissue with foci of hematopoietic cells. A case is presented of a seventy-one-year-old woman in whom the diagnosis was established preoperatively by means of sonography, computerized tomography, and magnetic resonance tomography. In a review of the literature, the radiologic profile is discussed, and based on the analysis of 59 surgically treated cases a therapy recommendation is given.

Adult Wilms' tumor: clinical and radiographic features

The clinical and radiographic features of Wilms' tumor in 4 adult patients are described. Wilms' tumors in adults are usually bulky and contain numerous areas of necrosis and hemorrhage, imparting a complex appearance to the lesion on sonography and computed tomography. Angiography reveals the tumor to be hypovascular with some neovascularity. No specific features of the lesion differentiate it from hypernephroma. In contrast to the childhood variety, Wilms' tumors in adults have ill-defined margins and frequently extend into the retroperitoneum. Their treatment is the subject of debate and prognosis is poor.