Malignant-appearing cells in pleural effusion due to pancreatitis: case report and literature review.

Malignant-appearing mesothelial cells were noted in an amylase-rich pleural effusion caused by pancreatitis in the absence of any neoplastic disease. Such changes in the mesothelial cells are believed to be the result of intense irritation of the serosal surfaces by the pancreatic enzymes. Review of the literature showed a likelihood of false-positive cytologic diagnosis of 0.44% for pleural effusions and 0.91% for all serous effusions. Because of the potential for serious error in patient management based on a false-positive cytology, it is important to recognize the conditions that may be responsible for it.