Case Report: A case of intrahepatic papillary neoplasm of the bile duct with invasive carcinoma in a young patient and review of the literature.

Introduction: Intrahepatic papillary neoplasm of the bile duct (IPNB) with invasive carcinoma is a rare cholangiocarcinoma with the most frequent site of origin being intrahepatic bile ducts. Given its rarity and non-specific clinical presentations, accurate diagnosis plagues clinicians to improve patient outcomes. Case presentation: We present a case of a 31-year-old male who initially exhibited fever. Routine ultrasonography and computed tomography (CT) revealed a large mass in the right liver lobe, suggesting a high likelihood of an infectious lesion. However, multidisciplinary discussion offered a variety of possible scenarios. The patient subsequently underwent an extended right hepatectomy (ERH), and histopathological examination suggested a intrahepatic IPNB with invasive adenocarcinoma. Clinical discussion: The diagnosis and management of IPNB remain challenging, particularly in patients who present with atypical clinical symptoms and lack significant abnormalities in laboratory tests. Early imaging plays a critical role in guiding the diagnostic process. However, comprehensive diagnostic speculations, clinical expertise, and even invasive detections are essential for establishing a definitive diagnosis and determining the appropriate treatment strategy. Given the potential to invasive carcinoma, early detection and resection are vital to improving prognosis.