Mucinous cystic neoplasm of the liver with biliary communication: a great imitator, diagnostic dilemma and surgical challenge

Mucinous cystic neoplasms of the liver (MCN-L) are rare tumours. We report a challenging case initially characterized as hydatid cyst. The patient underwent initial pericystectomy converted to completion left hepatectomy for definitive management. Histopathology confirmed MCN-L with focal high-grade dysplasia. Crucially, the resection specimen revealed a previously unrecognized finding: direct cyst rupture into the biliary tree, associated with bile encrustation, calculi formation, and inflammation. This case highlights that MCN-L can clinically and radiologically mimics other cystic liver lesions, necessitating histopathology for definitive diagnosis. The phenomenon of biliary communication and its sequelae are not readily accounted for in the current World Health Organization essential diagnostic criteria for MCN-L. Such cases may warrant the allowance of biliary communication within diagnostic criteria, to better reflect the spectrum of this lesion and avoid diagnostic pitfalls. Complete surgical excision is the mainstay of therapy, with long-term surveillance being essential, particularly in neoplasms with high-grade dysplasia.