OBJECTIVES The objectives of the study are (1) to distinguish lipoma (L) from atypical lipomatous tumor (ALT) using MRI qualitative features, (2) to assess the value of contrast enhancement, and (3) to evaluate the reproducibility and confidence level of radiological readings. MATERIALS AND METHODS Patients with pathologically proven L or ALT, who underwent MRI within 3 months from surgical excision were included in this retrospective multicenter international study. Two radiologists independently reviewed MRI centrally. Impressions were recorded as L or ALT. A third radiologist was consulted for discordant readings. The two radiologists re-read all non-contrast sequences; impression was recorded; then post-contrast images were reviewed and any changes were recorded. RESULTS A total of 246 patients (135 females; median age, 59 years) were included. ALT was histopathologically confirmed in 70/246 patients. In multivariable analysis, in addition to the lesion size, deep location, proximal lower limb lesions, demonstrating incomplete fat suppression, or increased architectural complexity were the independent predictive features of ALT; but not the contrast enhancement. Post-contrast MRI changed the impression in a total of 5 studies (3 for R1 and 4 for R2; 2 studies are common); all of them were incorrectly changed from Ls to ALTs. Overall, inter-reader kappa agreement was 0.42 (95% CI 0.39-0.56). Discordance between the two readers was statistically significant for both pathologically proven L (p < 0.001) and ALT (p = 0.003). CONCLUSION Most qualitative MR imaging features can help distinguish ALTs from BLs. However, contrast enhancement may be limited and occasionally misleading. Substantial discordance on MRI readings exists between radiologists with a relatively high false positive and negative rates.

中文翻译：

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对脂肪瘤和非典型脂肪瘤的MRI特征的定性评估：一项多中心研究的结果。

目的本研究的目的是（1）使用MRI定性特征将脂肪瘤（L）与非典型脂肪瘤（ALT）区别开来；（2）评估对比增强的价值；（3）评估可重复性和置信度放射学读数。材料与方法该回顾性多中心国际研究包括经手术切除后3个月内接受MRI病理证实的L或ALT的患者。两名放射线医师对中央MRI进行了独立检查。印象数记录为L或ALT。向第三位放射科医生咨询了不一致的读数。两位放射线医师重新读取了所有非造影剂序列。记录了印象；然后检查对比后的图像并记录任何更改。结果共有246位患者（135位女性；中位年龄 59年）。ALT在70/246例患者中被组织病理学证实。在多变量分析中，除病变大小，深处，下肢近端病变，脂肪抑制不完全或结构复杂性增加外，这些都是ALT的独立预测特征。但没有增强对比度。对比后MRI改变了总共5项研究的印象（R1为3项，R2为4项；常见2项研究）；他们都被错误地从Ls更改为ALTs。总体而言，读者之间的卡伯协议为0.42（95％CI为0.39-0.56）。经病理证实的L（p <0.001）和ALT（p = 0.003），两个阅读器之间的差异具有统计学意义。结论大多数定性的MR影像学特征可以帮助区分ALT和BL。然而，对比度增强可能会受到限制，并且有时会产生误导。放射科医师之间在MRI读数上存在很大差异，假阳性和阴性率相对较高。