From the Guidelines
Intraductal papillary mucinous neoplasms (IPMNs) of the pancreas are not always benign and should be considered as having malignant potential. These cystic lesions arise from the pancreatic ductal epithelium and produce mucin, ranging from benign to invasive carcinoma. The risk of malignancy varies based on several factors including location, size, and presence of concerning features such as mural nodules, dilated main pancreatic duct >10mm, or rapid growth 1.
Key Factors Influencing Malignancy Risk
- Location: main duct IPMNs have a higher risk of malignancy (around 62%) compared to branch duct IPMNs (<15%) 1
- Size: lesions >3cm pose a higher risk, with a positive predictive value for malignancy of 27-33% for cysts ≥30 mm 1
- Presence of concerning features:
- Mural nodules ≥5 mm
- Dilated main pancreatic duct ≥10 mm
- Rapid growth (>5 mm/year) 1
Management
Management typically involves surveillance with MRI/MRCP or endoscopic ultrasound for lower-risk lesions, while surgical resection is recommended for high-risk IPMNs 1. The decision between observation and surgery should be individualized based on patient factors including age, comorbidities, and surgical risk. Even after resection of benign IPMNs, long-term surveillance is necessary as patients have an increased risk of developing additional pancreatic lesions. The malignant transformation of IPMNs is believed to follow an adenoma-carcinoma sequence similar to colorectal cancer, progressing from low-grade dysplasia to high-grade dysplasia and eventually invasive carcinoma. Given the most recent and highest quality evidence, surgical resection is recommended for high-risk IPMNs, particularly those with main duct involvement, large size, or concerning features 1.
From the Research
Characteristics of Intraductal Papillary Mucinous Neoplasms (IPMNs)
- IPMNs represent approximately 1% of all pancreatic neoplasms and 25% of cystic neoplasms 2
- They are divided into three types: main duct-IPMN (MD-IPMN), branch duct-IPMN (BD-IPMN), and mixed type-IPMN 2
- The reported incidence of malignancy varies from 57% to 92% in the main duct-IPMN (MD-IPMN) and from 6% to 46% in the branch duct-IPMN (BD-IPMN) 3
Management of IPMNs
- Management depends on the type and radiological features of IPMNs 2
- Surgery is recommended for MD-IPMN 2, 4
- For BD-IPMN, management involves surgery or surveillance depending on the tumor size, cyst growth rate, solid components, main duct dilatation, high-grade dysplasia in cytology, the presence of symptoms, and CA 19.9 serum level 2
- Resection of all main duct IPMNs seems to be reasonable, and invasive IPMNs were associated with significantly worse survival than noninvasive IPMNs 4
Diagnosis and Surveillance
- Magnetic resonance imaging is the most useful for most IPMNs 2
- Magnetic resonance imaging (MRI) and endoscopic ultrasound (EUS) are primary investigations in diagnosing and following up on these patients 3
- The role of pancreatoscopy and the analysis of aspirated cystic fluid for cytology and DNA analysis is still to be established 3
- The follow-up of these patients could vary from 6 months to 1 year and would depend on the risk stratification for invasive malignancy and the pathology of the resected specimen 3