Undifferentiated Carcinoma With Osteoclast-like Giant Cells of the Pancreas Diagnosed by EUS-Guided Fine-Needle Biopsy.

Undifferentiated carcinoma with osteoclast-like giant cells of the pancreas is an extremely rare malignancy with nonspecific radiological features, often requiring histological confirmation. We report the case of a 57-year-old woman presenting with abdominal pain and cholestasis, in whom imaging revealed a pancreatic head mass. After an initial nondiagnostic endoscopic ultrasound sampling, endoscopic ultrasound-guided fine-needle biopsy performed at our tertiary referral center allowed definitive diagnosis by identifying characteristic osteoclast-like giant cells and undifferentiated neoplastic cells with a specific immunohistochemical profile. This case highlights the key role of endoscopic ultrasound-guided fine-needle biopsy in the preoperative diagnosis of undifferentiated carcinoma with osteoclast-like giant cells.