Comparison of Serum and Cyst Fluid CEA Levels in the Detection of Malignant or Mucinous Pancreatic Cysts

Abstract

Purpose: The serum level of carcinogenic embryonic antigen (CEA) has been reported to be elevated in a variety of tumors. It has been used to differentiate between benign and mucinous or malignant pancreatic cysts when measured in cyst fluid. However, the diagnostic value of this marker in serum is not clear in the evaluation of pancreatic cysts. The aim of this study is to determine the correlation of serum CEA and fluid CEA levels, particularly in the identification of mucinous or malignant pancreatic cysts. Methods: The endoscopic ultrasound (EUS) database was searched over a 36-month period and patients with cyst fluid CEA, serum CEA, and histology were selected for analysis. This included 46 patients with pancreatic cysts (22 female, 24 male; mean age 58.5 and 58.1 years, respectively). All patients underwent endoscopic ultrasound (EUS) - guided aspiration with fluid analysis including fluid amylase and CEA levels, and cytopathology. Serum CEA exceeding 5ng/mL and fluid CEA exceeding 192 ng/mL were deemed as elevated results. Results: In 42 of 46 patients, the serum CEA was normal. In 4 of 46 patients with elevated serum CEA, 3 (75%) had malignant or mucinous cysts. A total of 16 of 46 patients (34.8%) were found to have cytopathologic diagnosis of malignant or mucinous cysts. Of this subgroup, 3 (18.8%) had an elevated serum CEA (mean of 12.7 ng/mL) and 10 (62.5%) had elevated cyst fluid CEA (mean of 746.9 ng/mL). These results suggest that to predict the presence of a malignant or mucinous cyst, the serum CEA has 18.8% sensitivity, 96.7% specificity, 75% positive predictive value (PPV), and 69% negative predictive value (NPV). Differing from this, cyst fluid CEA has 62.5% sensitivity, 69% specificity, 52.6% PPV, and 77% NPV. The correlation between the serum and fluid CEA levels was poor. In the overall group, cyst fluid CEA was elevated in 19/46 patients (41%) of which only 4/19 (21%) had serum CEA elevations. Conclusion: Serum CEA level has an extremely poor sensitivity but markedly high specificity in comparison to cyst fluid CEA measurements in the detection of mucinous or malignant pancreas cysts. Serum and cyst fluid CEA levels also have poor correlation as evidenced by elevated serum levels noted in only 21% of patients with elevated cyst fluid CEA. This study suggests that a normal serum CEA has minimal utility while elevated serum CEA has a higher predictive value in the detection of such cysts. Cyst fluid CEA is an overall superior marker than serum CEA in this setting.