A Case of Resectable Single-Nodule Intrahepatic Bile Duct Adenoma.

A 70-year-old man was incidentally diagnosed with a single hepatic mass lesion in his right hepatic lobe during a computed tomography scan. The lesion exhibited consistent enhancement with contrast agents on computed tomography (CT), magnetic resonance imaging (MRI), and hepatic arterial angiography. While a definitive diagnosis could not be made preoperatively, the lesion was surgically resected due to its slight enlargement over two months, suggesting a potential malignancy. Pathological examination revealed the lesion to be a bile duct adenoma (BDA). The BDA was characterized by dense proliferative small gland cavities containing several to dozens of cells. Immunohistochemical staining showed positive CK7 and negative p53. The patient remains alive and free of recurrence five years after hepatectomy. Although BDAs are rare benign hepatic tumors, they carry a risk of harboring or developing malignant tissue, such as cholangiocarcinoma. Therefore, BDAs or lesions suspicious of BDA should be surgically resected or closely monitored.