Pallewatte Aruna S, Samarasinghe Eshma C
Department of Radiology, National Hospital of Sri Lanka, Colombo, Sri Lanka.
Indian J Radiol Imaging. 2021 Apr;31(2):472-475. doi: 10.1055/s-0041-1734332. Epub 2021 Jul 27.
Fibrolipomatous hamartoma is a rare nonhereditary, congenital condition characterized by benign hyperplasia of fibroadipose tissue around nerve bundles. The median nerve is commonly affected. Underlying pathological process is mature adipose and fibrous tissue infiltrating the epineural and perineural compartments giving typical "pseudo-onion bulb" appearance on histology and "coaxial cable" appearance on magnetic resonance imaging (MRI). This case of fibrolipomatous hamartoma well illustrates its characteristic clinical, radiological, and histopathological features. Patient is a teenage female presented with painless gradually enlarging mobile lump in the central left palm. Ultrasound scan revealed a hyperechoic subcutaneous lesion, with intervening fine hypoechoic cable like structures following the course of median nerve which was thickened. Computed tomography (CT) confirmed thickened left median nerve with radiating isodense fascicles surrounded by fatty areas. There were no calcifications. MRI showed classic "coaxial cable" like T1, T2 isointense fascicles continuous with the median nerve surrounded by a fusiform lesion demonstrating fat signals on spin-echo sequences which dropped on fat-suppressed gradient echo sequences. Diagnosis of fibrolipomatous hamartoma arising from left median nerve was made, based on typical imaging findings. Biopsy confirmed fibrolipomatous hamartoma. Diagnosis can be made confidently on imaging alone especially with MRI, without the need of biopsy. Both CT and MRI demonstrate fatty mass encasing the thickened nerve fibers. On MRI, characteristic appearance is seen as T1 and T2 low intense tubular thickened neural bundles surrounded by high signal fatty tissue.
纤维脂肪瘤性错构瘤是一种罕见的非遗传性先天性疾病，其特征为神经束周围纤维脂肪组织的良性增生。正中神经常受影响。潜在的病理过程是成熟的脂肪和纤维组织浸润神经外膜和神经束膜间隙，在组织学上呈现典型的“假洋葱球”外观，在磁共振成像（MRI）上呈现“同轴电缆”外观。该例纤维脂肪瘤性错构瘤很好地说明了其特征性的临床、放射学和组织病理学特征。患者为一名青少年女性，左手掌中央出现一个无痛性、逐渐增大的可移动肿块。超声扫描显示皮下高回声病变，其间有沿增厚的正中神经走行的细低回声条索状结构。计算机断层扫描（CT）证实左侧正中神经增厚，有放射状等密度束状结构，周围为脂肪区。无钙化。MRI显示典型的“同轴电缆”样T1、T2等信号束状结构与正中神经连续，周围为梭形病变，在自旋回波序列上显示脂肪信号，在脂肪抑制梯度回波序列上信号降低。根据典型的影像学表现，诊断为起源于左侧正中神经的纤维脂肪瘤性错构瘤。活检证实为纤维脂肪瘤性错构瘤。仅凭影像学尤其是MRI即可作出可靠诊断，无需活检。CT和MRI均显示脂肪肿块包绕增厚的神经纤维。在MRI上，特征性表现为T1和T2低信号的管状增厚神经束被高信号脂肪组织包绕。
