Risk of Malignancy Associated with the Diagnostic Categories Proposed by the Papanicolaou Society of Cytopathology for Pancreaticobiliary Specimens: An Institutional Experience

Background: The guidelines published by the Papanicolaou Society of Cytopathology (PSC) intend to unify the reporting language in pancreaticobiliary specimens and improve communication between cytopathologists and clinicians. The six categories in the system will determine the best management for patients. However, there is limited evidence regarding the risk of malignancy (ROM) associated with each category.

Methods: A retrospective search was performed for pancreaticobiliary fine-needle aspiration (FNA) reports with corresponding surgical follow-up. Cases were reclassified according to the PSC. The ROM, sensitivity, specificity, positive predictive value, and negative predictive value were calculated for each category.

Results: A total of 297 cases were identified and reclassified as: 30 nondiagnostic (category I), 45 negative for malignancy (II), 20 atypical (III), 42 neoplastic: other (IVB), 19 suspicious for malignancy (V), and 141 malignant (VI). The absolute ROM was 10% for category I, 8.9% for category II, 60% for category III, 4.8% for category IV when the neoplasms were not characterized as malignant, and 100% when categorized as malignant; 100% for category V, and 95.7% for category VI. Sensitivity, specificity, positive predictive value, and negative predictive value for neoplasia and malignancy, including categories IV to VI, were 96.6%, 88.4%, 97.5%, and 84.4%, respectively.

Conclusions: The categories developed by the PSC stratify the ROM. Aspirates designated as categories V and VI had the highest ROM. Our rate of atypical category complies with the recommended rate of <10%. This scheme provides valuable information to clinicians treating patients with pancreatic lesions.