E1689. Mechanisms of Spread of Hepatocellular Carcinoma
  1. Carla Harmath; University of Chicago
  2. Amir Borhani; Northwestern University
  3. Sabdeep Singh Arora; Yale University
  4. Mishal Mendiratta-Lala; University of Michigan
  5. Anil Dasyam; University of Pittsburgh
  6. Roberta Catania; Fondazione IRCCS Policlinico San Matte
  7. Katherine Frederick-Dyer; Vanderbilt University Medical Center
While low in prevalence (about 8% in some autopsy series), the incidence of extrahepatic metastasis detection in hepatocellular carcinoma (HCC) is increasing given longer survival with novel therapies. Detection of distant metastasis has implications on survival and choice of therapy.

Educational Goals / Teaching Points
The goals of our educational exhibit are to explain the different pathways of metastatic spread of hepatocellular carcinoma (HCC), their imaging spectrum, as well as recognition of patterns of metastatic spread related to targeted treatment. We will illustrate typical and atypical metastatic patterns and their treatment implications.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The presentation will include information on the diverse pathways of spread of hepatocellular carcinoma (HCC) such as hematogenous spread, lymphatic spread, direct invasion, post instrumentation and post-treatment disease progression. We will detail the pathophysiology and prevalence of each of the mechanisms. For hematogenous spread, typical and atypical patterns of extension by direct vascular invasion, including examples of classic vascular involvement such as portal venous - PV, hepatic venous- HV and inferior vena cava-IVC, and rare vascular involvement such as paraumbilical vein, right atrium will be provided. Typical and atypical patterns of distant hematogenous metastases, including classic (lung) and rare (mandibular metastasis) will also be included. For lymphatic spread, we will list the common and uncommon sites of involvement. Classic sites of nodal involvement, such as celiac and periportal, and less common sites such as retrocrural will be illustrated. Direct extrahepatic invasion, with most common pathway to the abdominal wall and peritoneum, and less common sites such as gallbladder and colon will be included. Post-instrumentation seeding and post-treatment disease progression will be discussed, including risk factors during biopsy and biopsy techniques – coaxial versus trocar, direct puncture versus through normal liver, fine needle aspiration (FNA) versus core biopsies and the practice of plugging the biopsy tract. Risk factors during ablation and technical points such as subcapsular tumor ablation techniques like direct puncture versus no touch wedge ablation, and needle tract cauterization will be discussed. In addition, the authors intend to comment on tumor necrosis and sloughing after embolic therapies, as well as assessment of diffusely infiltrative HCC after incomplete treatment.

Understanding the pathways of metastatic spread of HCC allows for increased attention to the detection of extrahepatic disease. This avoids unnecessary curative treatment options, and helps tailor the most adequate treatment for the patients.