Abstract: Objective:To summarize the MRI characteristics of fat-containing hepatocellular carcinoma (HCC).
Methods:The retrospective cross-sectional study was conducted. The clinicopathological 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 and iso-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^-3mm²/s, including (1.37±0.20)×10^-3mm²/s in lipid-rich type, (1.17±0.13)×10^-3mm²/s in clear cell type and (1.11±0.17)×10^-3mm²/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 microvascular 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.