Table 1. Summary of KLCA-NCC Practice Guidelines Version 2018 for Diagnosis of HCC.

Topic	Recommendations
Diagnosis of HCC	1) Diagnosis of HCC can be made with either pathology or noninvasive imaging in high-risk groups (CHB, CHC, or cirrhosis)
Diagnostic imaging modalities	2) In at-risk patients with lesion ≥ 1 cm in size on surveillance tests, multiphase CT or multiphase MRI with extracellular contrast agents or hepatobiliary contrast agents should be performed as first-line exam. If first-line imaging is inconclusive, second-line imaging examinations can be applied. Second-line imaging exams include multiphase CT, multiphase MRI with extracellular contrast agents or hepatobiliary contrast agents, and CEUS with blood pool contrast agents
Definite HCC	3) Imaging diagnosis can be applied to nodule ≥ 1 cm detected in at-risk patients during surveillance on basis of following radiologic hallmarks:
	(a) On multiphase CT or MRI with extracellular contrast agents, major imaging features for “definite” diagnosis of HCC are defined as APHE with washout in portal venous or delayed phases.
	(b) On multiphase MRI with hepatobiliary contrast agents, major imaging features for “definite” diagnosis of HCC are defined as APHE with washout in portal venous, delayed, or HBPs. These criteria should be applied only to lesion which does not show either marked T2 hyperintensity or targetoid appearance on DWI or CE sequences
Probable HCC	4) In nodule(s) with some but not all of aforementioned major imaging features of HCC, category of “probable” HCC can be assigned only when lesion fulfills at least one item from each of following two categories of ancillary imaging features. Two categories which make up ancillary imaging features are findings favoring malignancy in general (mild-to-moderate T2 hyperintensity, restricted diffusion, HBP hypointensity, interval growth) and those favoring HCC in particular (no-enhancing capsule, mosaic architecture, nodule-in-nodule appearance, fat or blood products in mass). These criteria should be applied only to lesion which shows neither marked T2 hyperintensity nor targetoid appearance on DWI or CE sequences
Follow-up	5) For “probable” HCC, follow-up imaging studies in less than 6 months or biopsy need to be considered to establish diagnosis. For indeterminate lesions, any changes in imaging patterns or serum tumor markers should be closely monitored, or biopsy can be considered for pathologic diagnosis
	6) In patients with subcentimeter-sized nodules, follow-up with interval of less than 6 months is recommended while closely monitoring interval growths or changes in imaging patterns
Recurred HCC	7) New or growing nodule which does not show typical imaging hallmarks of HCC found in follow-up of patient diagnosed with HCC could be diagnosed as HCC based on ancillary imaging features
Risk of radiation related to use of CT	8) Although strict limitation of radiation dose from CT for diagnosis and follow-up evaluation of HCC is not recommended, unnecessary radiation exposure from CT should be avoided. Techniques with reduced radiation dose and alternative imaging studies should be considered

APHE = arterial phase hyperenhancement, CE = contrast-enhanced, CEUS = contrast-enhanced ultrasound, CHB = chronic hepatitis B, CHC = chronic hepatitis C, CT = computed tomography, DWI = diffusion-weighted imaging, HBP = hepatobiliary phase, HCC = hepatocellular carcinoma, KLCA-NCC = Korean Liver Cancer Association-National Cancer Center, MRI = magnetic resonance imaging, US = ultrasound