Pancreatic Hepatoid Carcinoma Mimicking a Solid Pseudopapillary Neoplasm: A Challenging Case on Endoscopic Ultrasound-guided Fine-needle Aspiration

A 59-year-old man was admitted to our hospital for treatment of a 45 mm pancreatic mass found during a medical examination. Endoscopic ultrasound-guided fine-needle aspiration cytology showed polygonal cells with pseudopapillary structures. The tumor cells were positive for nuclear/cytoplasmic β-catenin and CD10, and negative for chromogranin A. After a tentative diagnosis of a solid pseudopapillary neoplasm, middle pancreatectomy was performed. Histologically, polygonal cells with abundant eosinophilic cytoplasm formed in the trabeculae and were immunohistochemically positive for HepPar1 and protein induced by vitamin K absence or antagonist-II. The tumor was finally diagnosed to be pancreatic hepatoid carcinoma. No recurrence occurred for 12 months, even without adjuvant chemotherapy.