含脂肝细胞癌MRI检查的影像学特征

MRI characteristics of fat-containing hepatocellular carcinoma

目的总结含脂肝细胞癌MRI检查的影像学特征。方法采用回顾性横断面研究方法。收集2015年1月至2016年4月第二军医大学东方肝胆外科医院收治的18例含脂肝细胞癌患者的临床病理资料。患者均行MRI检查，手术切除后肿瘤标本行病理学检查。观察指标：（1）影像学检查情况。（2）病理学检查结果。（3）治疗及随访。采用门诊影像学检查方式进行随访，术后1个月随访1次，以后每3个月随访1次；随访内容为肿瘤复发情况，随访时间截至2016年12月。正态分布的计量资料采用面±s表示。结果（1）影像学检查情况：MRI平扫显示：18例患者中，病灶位于肝左叶9例，肝右叶7例，肝尾状叶2例，病灶均为类圆形，直径为1．6～9．0cm。肿瘤均为单发，仅1例肉眼可见肝静脉癌栓：T2加权成像压脂表现为高信号15例，等信号3例；MRI检查均可见不同程度T1加权成像反相位较正相位信号下降．呈局灶性或弥漫性信号下降；T1加权成像脂相位示脂质弥漫性分布10例．含脂区域以斑片状散在分布于肿瘤周围区域7例，脂质位于中央区域1例。MRI动态增强扫描显示：18例患者中，快进快出型16例，快进慢出型1例，慢进慢出型1例；延迟期包膜样强化16例；弥散加权成像（DWI）显示高信号10例，稍高信号6例，等信号2例；表观弥散系数（ADC）值为（1．19±0．20）×10^-3mm2／s，其中富脂型ADC值为（1．37±0．20）×10^-3mm2／s，透明细胞型ADC值为（1．17±0．13）×10^-3mm2／s，粗梁型ADC值为（1．11±0．17）×10^-3mm2／s。18例患者中，术前2例误诊为肝血管平滑肌脂肪瘤，1例误诊为肝腺瘤。（2）病理学检查结果：18例含脂肝细胞癌患者病理学类型：富脂型5例，非富脂型13例（透明细胞型4例、粗梁型9例）：镜下均可见脂肪变性的肿瘤细胞，胞质丰富、透亮，可见大空泡状脂滴；脂肪变性肿瘤细胞弥漫或散在分布于病灶中，部分聚合呈大小不一斑块状表现；微血管浸润程度：M0级12例，M1级3例（2例粗梁型、1例透明细胞型），M2级3例（2例粗梁型、1例富脂型）。（3）治疗及随访：18例含脂肝细胞癌患者均行手术切除治疗，术后均获得随访，随访时间为6～13个月，中位随访时间为8个月。随访期间，5例富脂型和4例透明细胞型患者均未复发；9例粗梁型患者中，4例微血管浸润仅1例未复发，2例术后第3个月复发，1例术后第4个月复发，5例无微血管浸润者未见复发。3例复发患者均为单发复发灶，采用局部微创治疗．持续随访。结论含脂肝细胞癌MRI检查的影像学表现为T1加权成像反相位较正相位信号下降，DWI高信号，ADC值低，快进快出型强化方式，延迟期包膜样强化的特征性表现。

Objective： To summarize the MRI characteristics of fat-containing hepatocellular carcinoma （HCC）. Methods The retrospective cross-sectional study was conducted. The clinieopathological data of 18 patients with fat-containing HCC who were admitted to the Eastern Hepatobiliary Surgery Hospital of the Second Military Medical University between January 2015 and April 2016 were collected. All patients underwent MRI examination. Observation indicators ： （ 1 ） imaging examination ; （2） pathological features ; （ 3 ） treatment and follow-up. Follow-up using outpatient imaging examination was performed to detect tumor recurrence once at 1 month postoperatively and once every 3 months postoperatively up to December 2016. Measurement data with normal distribution were represented as ± s. Results （ 1 ） Imaging examination： plain scans of MRI： of 18 patients, lesions of 9, 7 and 2 patients were respectively located in left, right and caudate lobes of liver, and lesions were round-like, with a diameter of 1.6-9.0 cm. Tumors were single, and tumor thrombosis in the hepatic vein was seen in 1 patient. T2WI on fat-suppression of 15 and 3 patients showed respectively high signals andiso-signal; MRI examination showed that out-phase signal on T1WI was variously decreased than in-phase signal, showing focal or diffuse signal decreasing; lipid phase on T1WI showed diffuse distribution in 10 patients, patchy fat-containing regions were scattered within the peritumoral zone in 7 patients, and lipid of 1 patient was located in the central area. Dynamic contrast enhancement MRI showed that fast-in and fast-out, fast-in and slow-out, and slow-in and slow-out types were detected in 16, 1 and 1 patients, respectively. Sixteen patients had capsule-like enhancement in delayed phase. Diffusion weighted imaging （DWI） showed high signals in 10 patients, slightly high signals in 6 patients and iso-signal in 2 patients. Apparent diffusion coefficient （ADC） value was （ 1.19± 0. 20）×10^-3 mm2/s, including （ 1.37±0. 20） ×10^-3 mm2/s in lipid-rich type, （ 1.17±0. 13） ×10^-3 mm2/s in clear cell type and （1.11 ±0. 17）×10^-3 mm2/s in thick beam type. Of 18 patients, 2 were preoperatively misdiagnosed as hepatic angiomyolipoma and 1 as hepatic adenoma. （2） Pathological features： pathological types of 18 patients with fat-containing HCC： 5 and 13 patients were respectively in lipid-rich and non-lipid-rich types （4 in clear cell type and 9 in thick beam type） ; steatosis tumor cells, rich and translucent cytoplasms and large vacuolated lipid droplets were seen under the microscope ; steatosis tumor cells were diffused or scattered within the lesions, some of which showed plaque-like performance of different sizes. Degree of microvascular invasion ： grade M0, M1 and M2 were found in 12, 3 （2 in thick beam type and 1 in clear cell type） and 3 （2 in thick beam type and 1 in lipid-rich type） patients, respectively. （3） Treatment and follow-up： 18 patients underwent surgery and were followed up for 6-13 months, with a median time of 8 months. During the follow-up, 5 patients in lipid-rich type and 4 in clear cell type had no recurrence; among 9 patients in thick beam type, 1 of 4 with mierovascular invasion had no recurrence, 2 and 1 of 4 with microvascular invasion had respectively recurrence at 3 months postoperatively and 4 months postoperatively, and 5 without microvascular invasion had no recurrence. The lesions of 3 patients with recurrence is single, 3 patients received local minimally invasive therapy and continuous follow- up. Conclusion MRI characteristics of fat-containing HCC include that decreased out-phase signal on T1WI compared with in-phase signal, high signal on DWI, low ADC value, fast-in and fast-out enhancement and capsule-like enhancement in delayed phase.