Capsule, septum, and T2 hyperintense foci for differentiation between large hepatocellular carcinoma (≥5 cm) and intrahepatic cholangiocarcinoma on gadoxetic acid MRI

Objective: To determine the added value of capsule, septum, and T2 hyperintense foci for differentiating large hepatocellular carcinoma (HCC; ≥ 5 cm) from intrahepatic cholangiocarcinoma (ICC) using gadoxetic acid MRI. Methods: The study included 116 patients (94 men, 22 women; mean age, 56.8 years) with surgically confirmed HCCs (n = 87, 5.0–18.0 cm) or ICCs (n = 29, 5.0–14.0 cm) who underwent gadoxetic acid MRI. Three observers independently reviewed MRIs in two sessions, examining enhancement patterns only and then adding capsule, septum, and T2 hyperintense foci. Reviewers used a five-point scale to score accuracy, sensitivity, and specificity. Results: A significant increase was observed in accuracy when ancillary features (96.1–98.3%) were added compared to enhancement pattern only (83.6–88.4%; p ≤ 0.02). Sensitivity was significantly increased with combined reading (97.1–98.3%) compared to enhancement features only (81.6–88.5%; p ≤ 0.006) for two observers, with no difference in specificity (84.5–89.7% vs. 86.2–98.3%; p > 0.05). We found substantial to excellent interobserver agreement for ancillary features (0.598–0.976). Conclusion: Adding capsule, septum, and T2 hyperintense foci to enhancement patterns for gadoxetic acid MRI increased diagnostic performance for characterizing large HCC by differentiating it from ICC. Key Points: • Capsule, septum, and T2 hyperintense foci were useful for characterizing large HCC. • Adding ancillary features to enhancement pattern increased accuracy for diagnosing large HCC. • Interobserver agreement was substantial to excellent for ancillary features.