Pancreatic Ductal Adenocarcinoma.

The most frequent indication for pancreatic fine-needle aspiration sampling is to confirm or exclude a pancreatic ductal adenocarcinoma (PDAC). PDAC is the most common malignant neoplasm of the pancreas, and the term pancreatic cancer typically connotes this entity. The conventional type of PDAC is a tubular adenocarcinoma, with a number of morphological variations described. Morphologically distinct but related entities include adenosquamous carcinoma, undifferentiated carcinoma, and undifferentiated carcinoma with osteoclast-type giant cells. Unrelated carcinomas with ductal lineage include colloid carcinoma and medullary carcinoma. Less commonly reported carcinomas include signet ring cell carcinoma, hepatoid carcinoma, and oncocytic carcinoma. Here we will focus on the cytological findings of PDAC and other carcinomas of ductal lineage, briefly touching upon their clinical features, histologic appearance, and clinically useful serum markers. The differential diagnosis, pitfalls, and useful ancillary studies will also be reviewed. A diagnosis of PDAC should not be taken lightly given that it can potentially result in a pancreatic resection. Familiarity with the entities described in this review will help practicing cytopathologists confront these cases with appropriate information needed in order to render a clinically valuable diagnosis.