[433] False Positives in Pancreatic Cytopathology: The Role of Pancreatic Intraepithelial Neoplasia and Acute Pancreatitis

LJ Layfield, EA Jarboe. University of Utah School of Medicine, Salt Lake City, UT

Background: Fine-needle aspiration (FNA) has played a significant role in the diagnosis of pancreatic masses. Overall sensitivity is between 76 and 91 percent while specificity ranges from 84 to 100 percent. To better understand the etiology of false positive diagnoses, we reviewed our experience with false positive cytologic diagnoses of pancreatic adenocarcinoma.
Design: The Anatomic Pathology files were searched for all FNAs of pancreas with subsequent resections. Cases with a diagnosis of positive for or suspicious for adenocarcinoma followed by a resection specimen not showing adenocarcinoma were reviewed and correlations between the surgical pathology and cytology findings were made.
Results: Five cases had a cytologic diagnosis of adenocarcinoma or suspicious for adenocarcinoma but resection specimens did not confirm the diagnoses. In two cases, a non-invasive intraductal papillary mucinous neoplasm (IPMN) without significant dysplasia was present with foci of pancreatic intraepithelial neoplasia (PanIN). In both cases, the degree of atypia within the IPMN was less than that seen cytologically. The nuclear features of the PanIN overlapped those seen in the smears interpreted as adenocarcinoma. In a single case, a neuroendocrine neoplasm was present accompanied by multifocal PanIN. The cytologic features of the neuroendocrine neoplasm did not correlate with the material cytologically diagnosed as high grade dysplasia or adenocarcinoma. The cytologically atypical ductal epithelium corresponded closely to that seen in the PanIN. Two diagnoses of adenocarcinoma were made cytologically but the pancreatectomy specimens revealed pancreatitis with reactive atypia of ductal epithelium. The marked atypia seen histologically in the ductal epithelium corresponded to epithelial cells cytologically misinterpreted as adenocarcinoma.
Conclusions: The cytologic diagnosis of high grade pancreatic adenocarcinoma has high specificity. Cytologic separation of well differentiated adenocarcinomas from other lesions is less accurate. Five cytologic misdiagnoses occurring in 105 cases undergoing pancreatectomy. These misdiagnoses correlated with histopathologic changes of intermediate to high grade PanIN or marked reactive atypia in a background of severe pancreatitis. While reactive atypia in the setting of chronic pancreatitis is well recognized as a potential cause of false positive cytology, PanIN may be an under recognized, but significant source of false positive results.
Category: Cytopathology

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 40, Wednesday Afternoon


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