A 55-year-old man with a 3 cm pancreatic head mass has obstructive jaundice. CT shows a hypodense mass with pancreatic duct dilatation. Endoscopic ultrasound-guided biopsy shows mucin-producing columnar epithelium with moderate dysplasia within a dilated main pancreatic duct. No invasive carcinoma is seen. Which precursor lesion is this, and what is its cancer risk?

• A Main duct intraductal papillary mucinous neoplasm (MD-IPMN) with moderate dysplasia — carries high malignant potential (40-70% risk of harboring or developing invasive carcinoma) and warrants surgical resection ✓
• B Pancreatic intraepithelial neoplasia (PanIN-2) — very low risk of progression to invasive cancer; surveillance interval of 5 years is appropriate
• C Mucinous cystic neoplasm (MCN) — resection is mandatory only if calcifications or mural nodules are present; moderate dysplasia alone does not mandate surgery
• D Serous cystic neoplasm — invariably benign; the mucin-producing cells indicate serous cystadenoma subtype that does not require resection

Explanation

Main duct IPMN (MD-IPMN) is defined as segmental or diffuse dilatation of the main pancreatic duct ≥5 mm, caused by mucinous epithelial proliferation within the duct. Unlike branch duct IPMNs (which have lower malignant potential and may be surveilled), MD-IPMNs carry a 40-70% risk of associated invasive carcinoma and are generally resected regardless of dysplasia grade per Fukuoka/ISGP guidelines. PanIN lesions are microscopic (<5 mm) and not visible on imaging. MCNs occur predominantly in women, have an ovarian-type stroma, and do not communicate with the duct. Serous cystadenomas are composed of glycogen-rich clear cells, not mucin-producing columnar cells.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.