Mesenchymal hamartoma of the liver in a young adult female: a diagnostic challenge mimicking hepatic adenoma

Mesenchymal hamartoma of the liver (MHL) is a rare benign lesion usually seen in infants and young children; adult onset is exceptional and can mimic a broad spectrum of hepatic neoplasms on imaging, including hepatocellular, cholangiocytic/biliary, and mesenchymal tumors. A 31-year-old woman was found to have a 23-mm hyperechoic mass in segment 7 on screening ultrasonography. One year later, it had enlarged to 68 mm. Contrast-enhanced computed tomography showed a well-circumscribed 75-mm lesion with gradual heterogeneous enhancement. Given her >10-year history of oral contraceptive use, a benign hepatocellular tumor such as hepatocellular adenoma was suspected; however, biliary epithelial tumors and mesenchymal tumors were also considered in the differential diagnosis. Because of rapid growth and proximity to the right hepatic vein, robot-assisted extended posterior sectionectomy with right hepatic vein resection was performed. Pathology revealed fibromyxoid stroma with spindle mesenchymal cells, irregular bile ducts, consistent with MHL without malignant change.