Comparison of Apparent Diffusion Coefficient Values on Diffusion-Weighted MRI for Differentiating Hepatocellular Carcinoma and Intrahepatic Cholangiocarcinoma

<b>Background and Objectives</b>: Accurate noninvasive differentiation between hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC) remains a clinical challenge. This study aimed to assess the dignostic performance of apparent diffusion coefficient (ADC) values from diffusion-weighted MRI in distinguishing between HCC and ICC, with histological confirmation as the gold standard. <b>Materials and Methods</b>: A retrospective analysis was performed on 61 patients (41 HCC, 20 ICC) who underwent liver MRI and percutaneous biopsy between 2019 and 2024. ADC values were measured from diffusion-weighted sequences (b-values of 0, 500, and 1000 s/mm²), and regions of interest were placed over solid tumor areas. Statistical analyses included <i>t</i>-tests, one-way ANOVA, and ROC curve analysis. <b>Results</b>: Mean ADC values did not differ significantly between HCC (1.09 ± 0.19 × 10^-3 mm²/s) and ICC (1.08 ± 0.11 × 10^-3 mm²/s). ROC analysis showed poor discriminative ability (AUC = 0.520; <i>p</i> = 0.806). In HCC, ADC values decreased with lower differentiation grades (<i>p</i> = 0.008, η² = 0.224). No significant trend was observed in ICC (<i>p</i> = 0.410, η² = 0.100). Immunohistochemical markers such as CK-7, Glypican 3, and TTF-1 showed significant diagnostic value between tumor subtypes. <b>Conclusions</b>: ADC values have limited utility for distinguishing HCC from ICC but may aid in HCC grading. Immunohistochemistry remains essential for accurate diagnosis, especially in poorly differentiated tumors. Further studies with larger cohorts are recommended to improve noninvasive diagnostic protocols.