A 62-year-old man with a history of chronic pancreatitis is found to have a cystic pancreatic lesion on CT. Endoscopic ultrasound with cyst fluid analysis shows elevated carcinoembryonic antigen (CEA >200 ng/mL) and mucinous fluid. Cyst cytology shows low-grade mucinous epithelium. The two main differential diagnoses for this cyst are mucinous cystic neoplasm (MCN) and intraductal papillary mucinous neoplasm (IPMN). The SINGLE feature that definitively distinguishes MCN from IPMN is:
- A MCN contains serous fluid with low CEA; IPMN contains mucinous fluid with high CEA
- B MCN occurs exclusively in the pancreatic head; IPMN affects the body and tail
- C MCN is invariably associated with KRAS mutation; IPMN shows GNAS mutation exclusively
- D MCN shows ovarian-type stroma on histology; IPMN lacks ovarian stroma and communicates with the pancreatic duct ✓
Explanation
The histological hallmark that definitively distinguishes mucinous cystic neoplasm (MCN) from IPMN is the presence of ovarian-type stroma (mesenchymal stroma with spindle cells expressing progesterone receptors, resembling ovarian cortical stroma) beneath the epithelial lining of MCN. This ovarian stroma is absent in IPMN. Additionally, MCN does NOT communicate with the main pancreatic duct, whereas IPMN by definition arises from and communicates with the ductal system (main duct, branch duct, or mixed). MCN predominantly affects middle-aged women in the body/tail. Both MCN and IPMN contain mucinous fluid with elevated CEA; both can harbour KRAS mutations. GNAS mutations are specific to IPMN (found in 40-65% of IPMNs, absent in MCN), providing a useful molecular marker.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.