The “mosaic” architecture of hepatocellular carcinoma (HCC) refers to a heterogeneous imaging appearance of the tumor due to multiple histologic components resembling the multicolor tiles of a mosaic (Fig 1) [1]. This presentation is more commonly encountered in large, progressed HCCs [1]. On contrast-enhanced CT and MR imaging studies, a HCC with mosaic architecture will appear as a large lesion with multiple compartments of different density, signal intensity, and enhancement, separated by septations and often delineated by an enhancing capsule [1, 2] (Fig. 2). While the enhancing nodules correspond to viable tumor, the non-enhancing components represent fat, necrosis or hemorrhage [3, 4] (Fig. 3), frequently more conspicuous on T1- and T2-weighted MR images. The internal fibrous septations show delayed enhancement on contrast-enhanced CT and MR imaging. Finally, the heterogeneous signal intensity of the lesion can also be seen on the images acquired during the hepatobiliary phase after injection of Gd-EOB-DTPA [2].