Biliary pseudo tumor associated with hepatic atrophy.

Area of Science:

• Hepatobiliary Pathology
• Surgical Pathology
• Gastroenterology

Background:

• Extensive ductular proliferation can present as a pseudo-tumorous lesion, mimicking well-differentiated cholangiocarcinoma.
• This entity is not well-described in existing medical literature.

Purpose of the Study:

• To evaluate the clinicopathologic features of reactive ductular proliferation that mimics cholangiocarcinoma.
• To differentiate these lesions from actual cholangiocarcinoma.

Main Methods:

• Retrospective analysis of four cases with reactive ductular proliferation mimicking cholangiocarcinoma.
• Detailed study of clinicopathological features, including gross examination, histology, and immunohistochemistry.
• Cases were identified from 1995 to 2024 across two major academic health institutions.

Main Results:

• Cases included explants and resections, with some showing liver atrophy, portal vein thrombosis, and cirrhosis.
• Histologically, lesions showed marked ductular proliferation but lacked significant cytologic atypia and mitotic activity.
• Immunohistochemistry revealed wild-type p53 and retained p16 and BAP1 expression.

Conclusions:

• Biliary pseudo-tumors associated with lobar atrophy can mimic cholangiocarcinoma both grossly and microscopically.
• Accurate diagnosis requires awareness of this phenomenon and careful integration of clinical, imaging, and subtle histological findings.