T. Higaki collected patient data, S. Yamazaki wrote the manuscript, M. Sugitani advised on pathological data, and T. Takayama supervised the manuscript.
Biliary intraepithelial neoplasia (BilIN) was newly defined by the WHO in 2010 and is characterized by biliary cell atypia with an intraductal papillary lesion. It is always found in the major bile duct, but not in liver parenchyma.
A 50-mm irregular tumor was detected in the paracaval portion of the hepatic caudate lobe of a 61-year-old man. He had undergone total gastrectomy for advanced gastric cancer 2 years earlier. The tumor had increased from 20 to 50 mm in the last 6 months. Abdominal CT showed an irregular hypo-enhanced tumor, with a honeycomb appearance inside the tumor. Diffusion-weighted MRI and PET showed that the tumor had malignant features, though no tumor markers were elevated. The tumor seemed to invade into the inferior vena cava (IVC) and hepatic veins. At operation, under side clamping of the IVC, a total of 10 cm of ventral side IVC was resected with the left liver. Pathologically, the tumor was an inflammatory pseudo-tumor that contained intermediate-grade BilIN of persistent liver parenchyma in the tumor.
The honeycomb appearance within the tumor showed a causal relationship between the pathological and etiological representations of BilIN. Considering BilIN avoids an unnecessary operation when we encounter atypical imaging findings of liver tumors.