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Gastrointestinal Imaging

E2816. Hepatocellular Adenoma Subtypes: Radiologic-Pathologic Correlation

Kehler D,  Yang G,  Zwart C,  Salomao M,  Silva A. Mayo Clinic, Phoenix, AZ

Address correspondence to D. Kehler (danielkehler81@gmail.com)

Background Information: Hepatocellular adenomas are often considered benign tumors; however, their propensity to hemorrhage and undergo malignant degeneration significantly impacts patient management. Historically, these tumors were diagnosed with percutaneous biopsy or surgery because of the widely variable imaging appearance. Furthermore, even with a pathologically proven diagnosis, it is difficult to predict which tumors are bad actors. Over the last decade, technical advances have permitted identification of specific histopathologic and genetic features that help predict tumor behavior. Based on these features, four subgroups of hepatocellular adenoma have been characterized, each with a unique MRI appearance. Through a retrospective analysis of 95 patients with pathologically proven hepatocellular adenoma since January 1, 2010, we will demonstrate several MRI examples from each subtype and discuss the clinical implications.

Educational Goals/Teaching Points: The goal of this exhibit is to discuss specific histopathologic features and the basis for subclassification. Participants will be able to classify hepatic adenomas into one of four subtypes based on imaging features, show several pathologically proven examples of each subtype (inflammatory, hepatocyte nuclear factor 1 alpha [HNF1-a] mutated, ß-catenin mutated, unclassified), and discuss clinical implications of each subtype.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: Hepatic adenomas of the inflammatory subtype are the most common. Oral contraceptive pills (OCPs) and obesity are risk factors. Tumors of this subtype can present with a syndrome including fever, leukocytosis, as well as elevated liver function tests and inflammatory markers. This subtype has the highest propensity for hemorrhage and a small risk of malignant transformation (approx. 10%). Imaging findings appear diffusely isointense to slightly hyperintense on T1 and hyperintense on T2. Characteristic findings include intense arterial enhancement with persistent portal venous and delayed enhancement, and no diffuse signal drop on the opposed phase (may have focal signal drop). Hepatic adenomas of the HNF1-a subtype are the second-most common. They occur exclusively in women, and 90% of patients have a history of OCP use, and 50% of cases are multiple adenomas. These tumors have the most favorable prognosis of all subtypes (lowest risk for hemorrhage and malignancy of all adenomas). Imaging findings appear isointense or hyperintense on T1 and isointense to slightly hyperintense on T2. Characteristic findings include moderate arterial enhancement without persistent portal venous and delayed enhancement with diffuse signal drop on the opposed phase. Hepatic adenomas of the ß-catenin subtype are the third most common. They occur more frequently in men and are associated with exogenous male hormone administration, and has the highest association with malignant transformation. This subtype is associated with glycogen storage disease and familial adenomatosis polyposis syndrome. There are no consistent imaging features, but there may be a vague central scar. Findings may mimic hepatocellular carcinoma (strong arterial enhancement with washout). The unclassified subtype is the least common and has no consistent imaging features.

Conclusion: By recognizing and reporting the various subtypes of hepatocellular adenomas, we can better inform hepatology and surgical colleagues and significantly impact patient management.