Intraductal Papillary Mucinous Neoplasm (IPMN, Mucinous Duct Ectasia)

General: This is a rare subtype of mucin secreting pancreatic tumors. It is a mucinous epithelial tumor involving the pancreatic duct and/or its major branches, though may extend into smaller ducts, larger than a pancreatic intraepithelial neoplasm, and generally visible grossly and radiologically. Much better prognosis than pancreatic adenocarcinoma, despite being well described as a precancerous lesion with eventual (15~20 years) progression to adenocarcinoma.

Gross:

Microscopic:

• Adenoma: Tall columna mucin-containing cells with zero to mild dysplasia, but retains good differentiation.
• Borderline: Moderate dysplasia (some loss of polarity, nuclear crowding, nuclear enlargement, hyperchromasia, and pseudostratification. Papillary areas maintain identifiable stromal cores, though pseudopapillary structures may also be present.
• Carcinoma: Severe dysplastic epithelium (loss of polarity, diminished mucin content, pleomorphism, nuclear enlargement, mitoses (esp suprabasal or luminal), with or without invasion, and may be papillary or micropapillary. Cribriform architecture and budding of epithelial clusters into the lumen further suggest carcinoma.

Differential Diagnosis:

• Clinically and radiologically: Mucinous cystic neoplasm, retention cyst, pancreatitis.
• Histologically: Mucinous cystic neoplasm, retention cyst.

Stains:

• Positive:
• Negative:
• Suggested, focused panel:

((())) Am J Surg Pathol 2004;28(8):977-987., WHO.

Cases:

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