Pitfalls of extrahepatic bile duct cytology.

Cytological examination of extrahepatic bile ducts represents a challenging diagnostic field, often limited by sample quality and cellularity. Despite the availability of detailed classifications and cellular morphology descriptions, distinguishing benign from malignant lesions remains difficult in clinical practice. This paper reviews the current WHO classification system for pancreatobiliary cytopathology, with a focus on diagnostic categories specific to extrahepatic bile ducts. It discusses typical cytomorphological features, differential diagnoses, and the use of ancillary techniques such as immunohistochemistry and FISH, which may enhance diagnostic sensitivity and specificity. The importance of clinical context and interdisciplinary collaboration in cytological interpretation is emphasized.