Enhancement patterns and signal-intensity characteristics of small hepatocellular carcinoma in cirrhosis: pathologic basis and diagnostic challenges

Abstract

Recent pathologic studies of hepatic resection and transplantation specimens have elucidated the morphologic features of the precancerous lesions and small hepatocellular carcinomas (HCCs) arising in cirrhotic livers. Small HCCs measuring less than 2 cm in diameter are of two types: vaguely nodular, well-differentiated tumors, also known as "early" HCCs, and distinctly nodular tumors, with histologic features of "classic" HCC. The precancerous lesions include dysplastic foci and dysplastic nodules. "Classic" small HCCs are supplied by nontriadal arteries, whereas early HCCs and dysplastic nodules may receive blood supply from both portal tracts and nontriadal arteries. The similarities in blood supply of these three types of nodular lesions result in significant overlap of findings on dynamic imaging. Nevertheless, small HCCs sometimes display characteristic radiologic features, such as "nodule-in-nodule" configuration and "corona enhancement" pattern. Moreover, various histologic features of these nodular lesions may also be related to a variety of signal intensities and attenuation coefficients, while the presence of cirrhosis is known to limit the sensitivity and specificity of any imaging modality, due to liver inhomogeneity. Because of these reasons, imaging findings of nodular lesions in cirrhotic livers are often inconclusive, emphasizing the need for a better understanding of these imaging features.

CT and MR Imaging Diagnosis and Staging of Hepatocellular Carcinoma: Part II. Extracellular Agents, Hepatobiliary Agents, and Ancillary Imaging Features

“…This imaging appearance corresponds to the nodule-in-nodule growth pattern observed at histologic evaluation (130) and suggests the emergence of a progressed HCC within a dysplastic nodule or early HCC (131). The subnodule, corresponding to the progressed HCC, typically shows arterial phase hyperenhancement as well as hyperintensity on T2-weighted images (41) and, if a hepatobiliary agent is given, hypointensity in the hepatobiliary phase (Fig 8).…”

“…The surrounding parent nodule, corresponding to more well-differentiated tissue, typically is T1 hyperintense, T2 hypointense (132), and arterial phase hypo-or isoenhancing (85). The parent nodule may be fatty or iron rich (siderotic); the inner nodule usually contains less fat and, reflecting the iron "resistance" of neoplastic hepatocytes, less iron (133), While nodule-in-nodule configuration is characteristic of HCC, it is seen infrequently at CT and MR imaging (131), and the sensitivity and specificity of this feature for the diagnosis of HCC has not been established.…”

“…Although heterogeneity is a common characteristic of many liver lesions, mosaic architecture is unusual in tumors other than HCC, and so this feature helps in the differentiation of HCC from ICC. As mosaic architecture is uncommon in small HCCs (46,131), the incremental value of this in 77% of HCCs larger than 3 cm (136). By comparison, cirrhotic nodules and dysplastic nodules characteristically are isointense or hypointense on T2-weighted images and rarely show mild-moderate T2 hyperintensity (137).…”

Outcome of hypovascular hepatic nodules revealing no gadoxetic acid uptake in patients with chronic liver disease

“…As an early HCC progresses to overt HCC, the intratumoral vascularity increases (2)-a process referred to as ''hypervascularization'' in this study. Upon hypervascularization, HCCs exhibit a nodule-in-nodule appearance and are considered to be in the early-to-advanced stage (3)(4)(5).…”

Noninvasive Diagnosis of Hepatocellular Carcinoma in Cirrhotic Liver: Current Guidelines and Future Prospects for Radiological Imaging

“…Carcinogenesis of HCC in cirrhotic livers mirrors a continuous development from dysplastic foci to clonal expansion [3]. Typically, transformation continues from very small heterogeneous lesions with foci of highly differentiated carcinoma cells to poorly differentiated larger tumor nodules [4][5][6].…”