Biliary Hamartoma: An Unusual Cause of Liver Mass in Chronic Hepatitis B

Abstract

Introduction: Biliary hamartomas are benign liver malformations that are rare and are often confused with metastatic disease of the liver on imaging. They can also be difficult to distinguish from primary hepatocellular carcinoma in patients with cirrhosis. We present the case of a patient with chronic hepatitis B without documented cirrhosis who was found to have an incidental solitary liver lesion with biopsy revealing biliary hamartoma. Case Report: 69 y/o Asian male with h/o chronic hepatitis B was treated for 48 weeks with Pegasys prior to being lost to follow-up. He was recently diagnosed with prostate cancer at an outside facility and underwent TURP. As part of the work-up, he had a CT abdomen done prior to surgery to evaluate for any metastatic disease. He was found to have a low attenuated 2cm lesion in the Right lobe of the liver just beneath the capsule without any contrast enhancement. Alpha feto protein (AFP) level was normal at the time. On a subsequent follow-up CT 6 months later, the lesion had remained stable and did not increase in size. He had a CT abdomen done 4 years prior to current presentation, which had shown multiple low density lesions that were less than 1 cm and difficult to characterize. On current evaluation, patient did not have any stigmata of chronic liver disease. AFP level was normal. Biopsy of the right hepatic mass was performed and showed a biliary hamartoma in the setting of chronic hepatitis. The patient has been scheduled for 6 month follow-up imaging with MRI abdomen. Biliary hamartomas are congenital bile duct malformations that contain cystic dilated bile ducts surrounded by fibrous stroma and occur due to failure of embryonic involution. They are also called Von Meyenburg complexes (VMC's) named after the person who first described them. They are usually scattered throughout the liver especially in the subcapsular region. Biliary hamartomas are benign but malignant change to cholangiocarcinoma has been reported. Radiographically, they can present as a single mass or several nodules. When typical imaging findings appear, such as small comet-tail echoes on ultrasound, multiple tiny hypodense lesions with no enhancement on CT, and cystic appearance with normal extra and intrahepatic bile duct on MRI and MRCP, a diagnosis of biliary hamartoma or VMCs can be considered. Usual biliary hamartomas present as small, non-enhancing nodules in liver. However, in some cases, it can presents as a single solid or cystic mass with various contrast enhancement pattern. When a single or large hamartoma is seen as in our patient, its radiological diagnosis is difficult and the lesion is confused with metastasis. Hence, biopsy is required to confirm the diagnosis.