E1334. Tricks of the Trade: Lessons on Diagnosing Difficult Liver Lesions
  1. Carla Harmath; The University of Chicago
  2. Natally Horvat; Memorial Sloan Kettering Cancer Center
  3. Sandeep Arora; Yale School of Medicine
  4. Amita Kamath; Mount Sinai
  5. Robert Marks; Naval Medical Center
  6. Khaled Elsayes; MD Anderson Cancer Center
Hepatic lesions are usually characterized based on their appearance in relationship to the background hepatic parenchyma. Typical lesions can therefore have a different appearance when the background parenchyma is not normal. In addition, unusual or indeterminate lesions can have features that can help favor a benign or a malignant process. Characterizing hepatic lesions in the setting of an abnormal hepatic parenchyma, and guiding clinicians on how to proceed when an atypical lesion is encountered can be challenging.

Educational Goals / Teaching Points
The teaching objectives of this educational exhibit are to illustrate the unusual appearance of common liver lesions, to address the relationship of liver background parenchyma and the consequences on the relative appearance of a liver lesion and to troubleshoot a lesion with an indeterminate appearance on computed tomography (CT) and magnetic resonance imaging (MRI). The presentation will include an introduction and background, as well as guidance on how to evaluate lesions on CT and MRI. The differences in the background hepatic parenchyma, such as iron and fat deposition and how they can affect the appearance of a liver lesion will be addressed. The exhibit also intends to provide guidance on the imaging features favoring a benign process over a malignant etiology when facing an indeterminate hepatic lesion, and how to proceed. The utilization of different contrast agents in MRI and their value when characterizing liver lesions will be addressed, as well as troubleshooting their utility in patients with decreased hepatic parenchymal function.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The recognition of normal and abnormal background hepatic parenchyma on CT and MRI is necessary in order to adequately characterize a liver lesion. A lesion may not be as well visualized in the setting of background steatosis, for example, or may remain with apparent hyperenhancement to the parenchyma in such setting. Certain liver lesions and their pathophysiology can alter the appearance of the liver parenchyma, such as certain neuroendocrine metastases altering the triglyceride metabolism in the adjacent hepatocytes.

Understanding the hepatic background parenchyma and the pathophysiology of hepatic lesions are important factors for their accurate characterization.