Imaging Features of Primary Clear Cell Carcinoma of the Liver: A Case Series and Literature Review.

To analyse the computed tomography (CT) and magnetic resonance imaging (MRI) features of primary clear cell carcinoma of the liver (PCCCL), and to provide a diagnostic basis for its identification and differentiation from other lesions. Clinical and imaging data of five patients with surgically and pathologically confirmed PCCCL were retrospectively collected and analysed. All patients underwent non-contrast and dynamic contrast-enhanced CT and MRI scans. On non-contrast CT, all five lesions appeared hypodense, with the lowest CT attenuation values measured in the lesions within the negative range, suggestive of intralesional fat components. On MRI, T1-weighted imaging showed hypointensity in three cases, isointensity in one case, and mild hyperintensity in one case. T2-weighted fat-suppressed sequences revealed heterogeneous-both high and low-signals in four cases and mild hypointensity in one case. Dual-echo sequences demonstrated signal drop on opposed-phase images in all five cases. Diffusion-weighted imaging showed predominantly hypointense signals in one case and heterogeneous hyperintensity (predominantly hyperintense) in four cases. The apparent diffusion coefficient values were preserved in two cases but reduced in three cases. Dynamic contrast-enhanced imaging showed arterial phase enhancement in all five lesions, with washout to hypodense or hypointense patterns in the portal venous and delayed phases. Nodular enhancement was observed in one lesion, prominent intratumoral vessels in one case, and delayed capsular enhancement in two cases. Neither CT nor MRI revealed portal vein tumour thrombus, intrahepatic metastases, lymphadenopathy in the hepatic hilum or retroperitoneum, or ascites. PCCCL is a rare subtype of hepatocellular carcinoma. Identifying its distinct imaging findings, such as peripheral solitary lesions, intratumoral fat, and a high incidence of pseudocapsule formation, may enhance diagnostic accuracy.