[1857] Cystic Mucinous Duct Lesion of the Pancreas: A Clinicopathologic Analysis of 40 Examples of a Diagnostically Challenging and Terminologically Controversial Entity

Alyssa Krasinskas, Gerard J Oakley, Pelin Bagci, Kee-Taek Jang, Olca Basturk, Jeanette D Cheng, Leslie E Ducato, Charles E Hill, Ipek Erbarut, Volkan Adsay. UPMC, Pittsburgh; Emory University, Atlanta; MSKCC, New York; Piedmont Hospital, Atlanta

Background: Cystic pancreatic lesions that are ≥1cm and lined by non-papillary mucinous epithelium, variably termed “mucinous non-neoplastic cyst,” “retention cyst,” or “secondary ectasia” form a poorly characterized entity.
Design: 40 patients who underwent resection for such lesions were analyzed. Cysts detected incidentally during operations for other tumors were excluded.
Results: F/M:4. Mean age: 65 (22-85). Mean cyst size: 2.6 cm (1-8). All had a well defined paucicellular fibrous band surrounding the epithelium (0.5-3.5 mm). None had ovarian type stroma (PR negative in all 40). Most had innocuous appearing lining; attenuated in some areas, and all had at least partial mucinous lining, but without the papilla, undulation, tributary duct pattern of branch-duct IPMNs. The cyst lining showed focal high grade dysplasia in 3, intermediate in 17, but 21 had no significant atypia. Degenerative changes were common (26): hemorrhage, myxoid/hyalinized stroma in 16, calcification 4, histiocytic aggregates 12. No visible obstructive process (tm, pancreatitis, stones) to attribute the lesion to “secondary ectasia” was identified. Immunohistochemically (28 tested) the epithelium showed gastric differentiation (MUC5AC 79%, MUC6 93%, CK7 100%), but no intestinal differentiation (MUC2 0, CDX2 14%, CK20 4%). DPC4 was retained in all 20 tested. Foci of high ki-67 index (≥ 10%) were seen in 23%. P53 was positive in 4%. KRAS mutation was identified in tissue sections in only 4/19 however, 15/16 had mutation identified in the cyst fluid. Original diagnosis was IPMN in 10, MCN 6,“mucinous non-neoplastic cyst” 18, SCA 1, retention cyst 2, congenital cyst 1.
Conclusions: The fundamental lesion in these cases are cystic (mass forming), non-papillary version of PanIN-1A/mucinous duct lesion or a non-papillary (1A?) version of IPMN, for which cystic mucinous duct lesion (CMDL) would be the most appropriate term until their nature is further characterized. While the presence of degenerative changes and attenuated epithelium suggest a secondary ectasia (although no other cause of obstruction is demonstrable), preponderance for postmenopausal women suggests that these may be atrophic (regressed) version of MCNs. KRAS mutation is identified in the lining in 20%, and is commonly present in the cyst fluid, and further, there are foci of overt dysplasia in 48%, which warrants CMDL to be regarded neoplastic, albeit a very early (1A-type) lesion.
Category: Pancreas

Monday, March 19, 2012 8:45 AM

Platform Session: Section G1, Monday Morning

 

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