Ritchie D A, Aniq H, Davies A M, Mangham D C, Helliwell T R
Department of Radiology, Royal Liverpool and Broadgreen University Hospitals Trust, Prescott Street, Liverpool L7 8XP, UK.
Skeletal Radiol. 2006 Aug;35(8):579-89. doi: 10.1007/s00256-006-0114-4. Epub 2006 Apr 27.
OBJECTIVE, DESIGN AND PATIENTS: Hibernoma is an uncommon, slow-growing, benign soft-tissue tumour resembling brown adipose tissue. The histological appearances are well-documented, but there are relatively few descriptions of the magnetic resonance (MR) imaging features. We report a retrospective comparison of the histological and MR appearances of ten hibernomas of the extremities, classified histologically into lipoma-like [<70% multivacuolated adipocytes (MVAs)] and non-lipoma-like hibernomas (>70% MVAs).
The lipoma-like hibernomas measured 4-27 cm in maximum size. All were well-defined on MR imaging and histology except for one subcutaneous lesion that blended in with surrounding fat histologically. All lesions were isointense with subcutaneous fat on T1- and T2-weighting apart from one lesion that was predominantly slightly hypointense on T1-weighting and predominantly slightly hyperintense on T2-weighting and STIR. Two slightly inhomogeneous lesions contained thin (<5 mm thickness) tortuous vessels. One patient received intravenous contrast, but the lesion did not enhance. The six non-lipoma-like hibernomas measured 2.5-15.5 cm in maximum size and all were unencapsulated. Three were well-defined and three partly ill-defined on MR imaging. There were no significant differences in the MR characteristics of the non-lipoma-like variants. On T1-weighting, the non-lipoma-like hibernomas that contained >90% MVAs were predominantly slightly hypointense to subcutaneous fat. One lesion was isointense with subcutaneous fat, but this lesion only contained from 80-90% MVAs. All non-lipoma-like lesions were slightly hyperintense on STIR but so too were two of the four lipoma-like lesions. Four of the six non-lipoma-like lesions showed marked or moderate inhomogeneity due to thick septa and prominent vessels. Of the two cases that received intravenous contrast, both showed enhancement corresponding to regions of >90% MVAs or prominent vessels within fibrous septa.
MR imaging has shown some distinguishing features between lipoma-like and non-lipoma-like hibernomas. Lipoma-like hibernomas are usually isointense with subcutaneous fat on T1-weighting, are either homogeneous or slightly inhomogeneous and may contain thin tortuous vascular structures. Non-lipoma-like hibernomas are pre-dominantly slightly hypointense to subcutaneous fat on T1-weighting, often display marked or moderate inhomogeneity with prominent septa and vessels and enhancement is typical. The appearances of non-lipoma-like hibernomas are not diagnostic and may be mimicked by lipoma variants and by well-differentiated liposarcoma or atypical lipoma.
目的、设计与患者：冬眠瘤是一种罕见的、生长缓慢的良性软组织肿瘤，类似于棕色脂肪组织。其组织学表现已有充分记录，但关于磁共振（MR）成像特征的描述相对较少。我们报告了对10例四肢冬眠瘤的组织学和MR表现进行的回顾性比较，这些冬眠瘤在组织学上分为脂肪瘤样[多泡性脂肪细胞（MVA）<70%]和非脂肪瘤样冬眠瘤（MVA>70%）。
脂肪瘤样冬眠瘤最大尺寸为4 - 27厘米。除一个皮下病变在组织学上与周围脂肪融合外，所有病变在MR成像和组织学上均边界清晰。除一个病变在T1加权像上主要呈轻度低信号、在T2加权像和短TI反转恢复（STIR）序列上主要呈轻度高信号外，所有病变在T1和T2加权像上均与皮下脂肪等信号。两个轻度不均匀的病变含有薄（厚度<5毫米）的迂曲血管。一名患者接受了静脉造影剂注射，但病变未强化。6例非脂肪瘤样冬眠瘤最大尺寸为2.5 - 15.5厘米，均无包膜。3例在MR成像上边界清晰，3例部分边界不清。非脂肪瘤样变体的MR特征无显著差异。在T1加权像上，MVA>90%的非脂肪瘤样冬眠瘤主要比皮下脂肪轻度低信号。一个病变与皮下脂肪等信号，但该病变仅含有80 - 90%的MVA。所有非脂肪瘤样病变在STIR序列上均轻度高信号，但4例脂肪瘤样病变中的2例也是如此。6例非脂肪瘤样病变中有4例因厚间隔和明显血管而表现为明显或中度不均匀。在接受静脉造影剂注射的2例病例中，两者均显示对应于MVA>90%区域或纤维间隔内明显血管的强化。
MR成像显示了脂肪瘤样和非脂肪瘤样冬眠瘤之间的一些鉴别特征。脂肪瘤样冬眠瘤在T1加权像上通常与皮下脂肪等信号，要么均匀要么轻度不均匀，可能含有薄的迂曲血管结构。非脂肪瘤样冬眠瘤在T1加权像上主要比皮下脂肪轻度低信号，常表现为明显或中度不均匀，有明显的间隔和血管，典型表现为强化。非脂肪瘤样冬眠瘤的表现不具有诊断特异性，可能被脂肪瘤变体、高分化脂肪肉瘤或非典型脂肪瘤所模仿。
