Independent risk factors for true malignancy in atypical cytologic diagnostic category in EUS-FNA/FNB of the pancreas: A novel prediction model

BACKGROUND AND OBJECTS: An atypical cytologic diagnosis arises from inflammation or early neoplastic process. It is commonly found in EUS-guided fine-needle aspiration/biopsy (EUS-FNA/FNB) tissue sampling of pancreatic malignancies. The aims of this study were to evaluate the diagnostic performance of EUS-FNA/FNB in patients with cytologic diagnosis of atypical cells and to develop a prediction model for malignant tumors of the pancreas in the atypical cytologic diagnostic category. METHODS: Two hundred and twenty-six patients in the atypical cytologic diagnostic category were analyzed. Multivariate logistic regression analyses were performed to determine predictive factors for pancreatic malignancies. The final diagnoses were confirmed by repeat biopsy; surgical pathology, or clinical follow-up for at least 6 months. RESULTS: The atypical cytologic diagnosis using EUS-FNA/FNB was associated with an absolute risk of malignancy (82.3%). Multivariate logistic regression analyses revealed that older age, long axis of the mass, and increased carbohydrate antigen 19-9 (CA19-9) were independent risk factors for true malignant pancreatic tumors among patients in the atypical cytologic diagnostic category. The calibration curve had a slope of 0.96, and a regression coefficient (R(2)) of 0.91. The area under the receiver operating characteristic curve of the validation group was 0.803. CONCLUSIONS: Atypical lesions of EUS-FNA/FNB have a higher risk of malignancy. Older age, the long axis of the mass, and elevated serum CA19-9 level were identified as independent risk factors for true malignant pancreatic tumors among patients in the atypical cytologic diagnostic category.