A significant number of lipomas will have prominent non-adipose areas and will demonstrate an imaging appearance traditionally ascribed to well-differentiated liposarcoma. Features that suggest malignancy include increased patient age, large lesion size, presence of thick septa, presence of nodular and/or globular or non-adipose mass-like areas, and decreased percentage of fat composition.

Lipoma is the most common soft-tissue tumor, with a wide spectrum of clinical presentations and imaging appearances. Several subtypes are described, ranging from lesions entirely composed of mature adipose tissue to tumors intimately associated with nonadipose tissue, to those composed of brown fat. The imaging appearance of these fatty masses is frequently sufficiently characteristic to allow a specific diagnosis. However, in other cases, although a specific diagnosis is not achievable, a meaningful limited differential diagnosis can be established. The purpose of this manuscript is to review the spectrum of benign fatty tumors highlighting the current classification system, clinical presentation and behavior, spectrum of imaging appearances, and treatment. The imaging review emphasizes computed tomography (CT) scanning and magnetic resonance (MR) imaging, differentiating radiologic features.

Liposarcoma is a relatively common soft tissue malignancy with a wide spectrum of clinical presentations and imaging appearances. Several subtypes are described, ranging from lesions nearly entirely composed of mature adipose tissue, to tumors with very sparse adipose elements. The imaging appearance of these fatty masses is frequently sufficiently characteristic to allow a specific diagnosis, while in other cases, although a specific diagnosis is not achievable, a meaningful limited differential diagnosis can be established. The purpose of this paper is to review the spectrum of malignant fatty tumors, highlighting the current classification system, clinical presentation and behavior, treatment and spectrum of imaging appearances. The imaging review will emphasize CT scanning and MR imaging, and will stress differentiating radiologic features.

Despite tremendous technical advances in spine surgery in recent decades, patients may experience residual or recurrent pain and other symptoms after such surgery. The standard history and physical examination have only limited utility for assessing the postoperative anatomy, and radiologists can play an important role in diagnosing complications and guiding postoperative care. To do so effectively, they must be familiar with the imaging features of successful and unsuccessful fusion, instrumentation fracture and loosening, complications due to faulty hardware placement, and postoperative infection. A basic knowledge of spinal biomechanics and common approaches to surgical instrumentation also may help radiologists anticipate and identify complications.

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Although diagnosing gout generally is straightforward, atypical disease may present a challenge if it is associated with unusual symptoms or sites, discordant serum urate level, or mimics of gout. Dual-energy computed tomography (CT) may be used to differentiate urate crystals from calcium by using specific attenuation characteristics, which may help diagnose gout. In patients with known tophaceous gout, dual-energy CT may be used for serial volumetric quantification of subclinical tophi to evaluate response to treatment. Given the utility of dual-energy CT in challenging cases and its ability to provide an objective outcomes measure in patients with tophaceous gout, dual-energy CT promises to be a unique and clinically relevant modality in the diagnosis and management of gout.

The diagnosis of spindle cell lipoma should be suggested when a well-defined complex fatty mass is found in the subcutis of a middle-aged man, especially if the mass is localized to the posterior neck. Intense enhancement of the nonadipose component further supports this diagnosis.

Cherubism is a rare osseous disorder of children and adolescents. Although the radiologic characteristics of cherubism are not pathognomonic, the diagnosis is strongly suggested by bilateral relatively symmetric jaw involvement that is limited to the maxilla and mandible. Imaging typically shows expansile remodeling of the involved bones, thinning of the cortexes, and multilocular radiolucencies with a coarse trabecular pattern.