Multicystic biliary hamartoma with long-term gradual enlargement treated by laparoscopic partial hepatectomy.

Multicystic biliary hamartoma (MCBH) is an extremely rare liver tumor characterized by a well-circumscribed, multicystic honeycomb appearance on imaging. Herein, we report a case of long-term gradually enlarging MCBH that underwent laparoscopic hepatectomy. A 69-year-old man presented with mildly elevated carcinoembryonic antigen levels and underwent computed tomography (CT) 11 and 5 years ago, at which time the physicians did not note any particular abnormal findings. The current contrast CT for screening demonstrated a cystic lesion in segment 2 of the liver. A retrospective review of CT images showed that the cystic lesion had gradually increased over time. The patients successfully underwent laparoscopic partial hepatectomy and recovered without any complications. The surgically resected specimen grossly presented an aggregated nodule of small cysts. Pathological findings showed multiple cysts of various sizes covered with cuboidal cells without dysplasia resembling bile duct epithelium, with lumens containing a stone component consisting of brown bile. Around the cyst, there was vascular fibrous tissue, smooth muscle bundles, normal hepatocytes, and chronic inflammation. Based on these findings, we finally diagnosed MCBH. Although MCBH is histologically classified as a benign tumor, physicians may have to pay careful attention to the potential for enlargement in actual clinics.