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BACKGROUND. In LI-RADS version 2018, observations showing at least one of five targetoid appearances in different sequences or postcontrast phases are categorized LR-M, indicating likely non-hepatocellular carcinoma (HCC) malignancy. OBJECTIVE. The purpose of this study was to evaluate interobserver agreement for LI-RADS targetoid appearances among a large number of radiologists of varying experience and the diagnostic performance of targetoid appearances for differentiating HCC from non-HCC malignancy. METHODS. This retrospective study included 100 patients (76 men, 24 women; mean age, 58 ± 9 [SD] years) at high risk of HCC who underwent gadoxetic acid-enhanced MRI within 30 days before hepatic tumor resection (25 randomly included patients with non-HCC malignancy [13, intrahepatic cholangiocarcinoma; 12, combined HCC-cholangiocarcinoma]; 75 matched patients with HCC). Eight radiologists (four more experienced [8-15 years]; four less experienced [1-5 years]) from seven institutions independently assessed observations for the five targetoid appearances and LI-RADS categorization. Interobserver agreement and diagnostic performance for non-HCC malignancy were evaluated. RESULTS. Interobserver agreement was poor for peripheral washout (κ = 0.20); moderate for targetoid transitional phase or hepatobiliary phase appearance (κ = 0.33), delayed central enhancement (κ = 0.37), and targetoid restriction (κ = 0.43); and substantial for rim arterial phase hyperenhancement (κ = 0.61). Agreement was fair for at least one targetoid appearance (κ = 0.36) and moderate for at least two, three, or four targetoid appearances (κ = 0.43-0.51). Agreement for individual targetoid appearances was not significantly different between more experienced and less experienced readers other than for targetoid restriction (κ = 0.63 vs 0.43; p = .001). Agreement for at least one targetoid appearance was fair among more experienced (κ = 0.29) and less experienced (κ = 0.37) reviewers. Agreement for at least two, three, or four targetoid appearances was moderate to substantial among more experienced reviewers (κ = 0.45-0.63) and moderate among less experienced reviewers (κ = 0.42-0.56). Existing LR-M criteria of at least one targetoid appearance had median accuracy for non-HCC malignancy of 62%, sensitivity of 84%, and specificity of 54%. For all reviewers, accuracy was highest when at least three (median accuracy, 79%; sensitivity, 68%; specificity, 82%) or four (median accuracy, 80%; sensitivity, 54%; specificity, 88%) targetoid appearances were required. CONCLUSION. Targetoid appearances and LR-M categorization exhibited considerable interobserver variation among both more and less experienced reviewers. CLINICAL IMPACT. Requiring multiple targetoid appearances for LR-M categorization improved interobserver agreement and diagnostic accuracy for non-HCC malignancy.

Objective: The purpose of this study was to examine the associations between preoperative Liver Imaging Reporting and Data System (LI-RADS) categories and prognosis after curative resection of single hepatic malignancies in patients with chronic liver disease., Materials and Methods: Between January 2008 and December 2010, 225 patients with chronic liver disease underwent resection of single hepatic malignant tumors (218 hepatocellular carcinomas, three cholangiocarcinomas, four biphenotypic carcinomas) after undergoing gadoxetic acid-enhanced MRI. Two radiologists retrospectively categorized the tumors into LI-RADS categories. Differences in disease-free survival duration between categories were analyzed by the Kaplan-Meier method with the log-rank test., Results: Reviewer 1 categorized two (0.9%) patients as having LR-3, 53 (23.6%) LR-4, 159 (70.7%) LR-5, and 11 (4.9%) LR-M lesions. The corresponding numbers for reviewer 2 were six (2.7%) LR-3, 30 (13.3%) LR-4, 178 (79.1%) LR-5, and 11 (4.9%) LR-M. The 2-year cumulative recurrence or death rates were 15.1% for lesions categorized LR-3 or LR-4 by reviewer 1, 31.7% for LR-5, and 60% for LR-M. For lesions categorized by reviewer 2 the corresponding rates were 20.6% for LR-3 or LR-4, 29% for LR-5, and 54.5% for LR-M. Disease-free survival was significantly worse among patients with lesions categorized as LR-M than for lesions categorized as LR-3 or LR-4 or as LR-5 (p < 0.01 for both reviewers). Disease-free survival did not significantly differ between patients with LR-3 or LR-4 and those with LR-5 lesions (reviewer 1, p = 0.301; reviewer 2, p = 0.291)., Conclusion: Patients with tumors preoperatively categorized as LR-M may have a worse prognosis than those with tumors categorized LR-3, LR-4, or LR-5 after curative resection of single hepatic malignancy.