Abstract
BackgroundTo evaluate the diagnostic value of MR imaging for the differentiation of lipomas and atypical lipomatous tumors (ALT) in comparison with histology and MDM2 amplification status.MethodsPatients with well-differentiated lipomatous tumors (n = 113), of which 66 were diagnosed as lipoma (mean age 53 years (range, 13–82); 47% women) and 47 as atypical lipomatous tumor (ALT; mean age 60 years (range, 28–88); 64% women), were included into this study using histology and MDM2 amplification status by fluorescence in situ hybridization (FISH) as standard of reference. Preoperative MR images were retrospectively assessed by two radiologists for the following imaging features: maximum tumor diameter (mm) as well as the affected compartment (intramuscular, intermuscular or subcutaneous), septa (absent, thin (< 2 mm) or thick septa (> 2 mm) with nodular components); contrast enhancing areas within the lipomatous tumor (< 1/3 of the tumor volume, > 1/3 of the tumor volume);ResultsOf the 47 patients with ALT, 40 (85.1%) presented thick septa (> 2 mm) and this finding significantly increased the likelihood of ALT (OR 6.24, 95% CI 3.36–11.59; P < 0.001). The likelihood of ALT was increased if the tumor exceeded a maximum diameter of 130.0 mm (OR 2.74, 95% CI 1.82–4.11, P < 0.001). The presence of contrast enhancement in lipomatous tumors significantly increased the likelihood of ALT (Odds ratio (OR) 2.95, 95% confidence interval (CI) 2.01–4.31; P < 0.001). Of the lipomas, 21.1% were located subcutaneously, 63.6% intramuscularly and 15.2% intermuscularly. On the other hand, none of the ALTs were located subcutaneously, the majority was located intermuscularly (87.3%) and a small number of ALTs was located intramuscularly (12.7%).ConclusionsOur results suggest that using specific morphological MR imaging characteristics (maximum tumor diameter, thick septa and contrast enhancement) and the information on the localization of the lipomatous tumor, a high sensitivity and substantial specificity can be achieved for the diagnosis of lipomas and ALTs.
Highlights
To evaluate the diagnostic value of magnetic resonance (MR) imaging for the differentiation of lipomas and atypical lipomatous tumors (ALT) in comparison with histology and MDM2 amplification status
Previous magnetic resonance imaging studies have described that the presence of certain characteristics, such as the size of lipomatous tumors, thick septa and reduced fat content increased the likelihood of the diagnosis of ALT [13, 20, 21]
In a receiver operating characteristic (ROC) analysis of the maximum tumor size, the area under the curve (AUC) for the differentiation of the two entities was 0.809, with an optimal cut-off value of 130.0 mm (J, 0.505; sensitivity, 0.809; specificity, 0.697). Using this cut-off value, the likelihood of a tumor to be an ALT was increased by a factor of 2.74 if it had a Discussion Our study focused on assessing MR imaging features of lipomas and ALTs in order to differentiate between the two entities, using a combination of histology and genetic testing as a standard of reference
Summary
To evaluate the diagnostic value of MR imaging for the differentiation of lipomas and atypical lipomatous tumors (ALT) in comparison with histology and MDM2 amplification status. Lipomatous tumors are the most common type of soft tissue tumors of the extremities The majority of these tumors are atypical lipomatous tumors (ALT) or lipomas [1,2,3], representing 40 to 45% of the lipomatous tumors [4, 5]. It was previously demonstrated that lipomas were often over-diagnosed if the pathological diagnosis was based on histology only, since many lipomatous tumors that were histologically considered to be lipomas showed a positive MDM2 amplification status in the cytogenetic analysis, which is a marker highly sensitive for ALT [22]
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