A case of non-exposed ampullary carcinoma diagnosed by EUS-FNA after a prolonged clinical course

An 81-year-old woman presented with liver dysfunction. Endoscopic retrograde cholangiopancreatography revealed a distal bile duct stricture, raising suspicion of malignancy. However, cytology and histology showed no evidence of malignancy, and repeated follow-up evaluations remained non-diagnostic. Thirty months after the initial presentation, she was hospitalized due to obstructive jaundice. Papillary traction was endoscopically observed at the time; however, as before, brush cytology and biopsy failed to confirm the presence of malignancy. Endoscopic ultrasound (EUS) revealed a faint hypoechoic mass at the site of the stricture, and EUS-guided fine-needle aspiration (EUS-FNA) yielded Class V cytology, establishing a definitive diagnosis. We present this diagnostically challenging case of non-exposed ampullary carcinoma in which conventional endoscopic procedures failed to detect the malignancy, thereby highlighting the usefulness of EUS-FNA as a definitive diagnostic tool.