Rethinking imaging-based IPMN subtype classification: is mixed-type a necessary radiologic category?

Area of Science:

• Gastroenterology
• Radiology
• Oncology

Background:

• Intraductal papillary mucinous neoplasms (IPMNs) are cystic neoplasms of the pancreas with malignant potential.
• Accurate classification of IPMN subtypes is crucial for risk stratification and management.
• Radiologic assessment of IPMN subtypes and main pancreatic duct (MPD) features are used to predict malignancy.

Purpose of the Study:

• To assess the concordance between radiologic and pathologic classification of IPMN subtypes.
• To evaluate interobserver agreement for IPMN subtype classification and MPD diameter measurement.
• To determine if IPMN subtype classification adds value for malignancy risk stratification beyond MPD features.

Main Methods:

• Retrospective review of 144 patients with surgically resected IPMN.
• Independent radiologic review of preoperative CT/MRI by two blinded radiologists.
• Adjudication of discrepancies and logistic regression/ROC analyses for malignancy prediction.

Main Results:

• Radiology-pathology concordance for IPMN subtype was 60.4%.
• Interobserver agreement was moderate for subtype (κ=0.509) but excellent for MPD diameter (ICC=0.909).
• MPD diameter independently predicted malignancy and outperformed subtype classification (AUC 0.737 vs. 0.624).

Conclusions:

• Radiologic IPMN subtype classification shows modest concordance and moderate interobserver agreement.
• MPD diameter is a more reliable predictor of malignancy risk.
• Focusing on MPD measurement may offer a more reproducible approach to IPMN risk stratification.