Mucinous nonneoplastic cyst of the pancreas: apomucin phenotype distinguishes this entity from intraductal papillary mucinous neoplasm

Cao, Wenqing; Adley, Brain P.; Liao, Jie; Lin, Xiaoqi; Talamonti, Mark; Bentrem, David J.; Rao, Sambasiva M.; Yang, Guang-Yu

doi:10.1016/j.humpath.2009.05.017

« Previous Next »Human Pathology
Volume 41, Issue 4 , Pages 513-521, April 2010

Mucinous nonneoplastic cyst of the pancreas: apomucin phenotype distinguishes this entity from intraductal papillary mucinous neoplasm☆

Wenqing Cao, MD
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
- These two authors contributed equally to this study.
Brain P. Adley, MD
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
- These two authors contributed equally to this study.
Jie Liao, MD
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
Xiaoqi Lin, MD, PhD
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
Mark Talamonti, MD
- Department of Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
David J. Bentrem, MD
- Department of Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
Sambasiva M. Rao, MD
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
- Corresponding authors.
Guang-Yu Yang, MD, PhD
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
- Corresponding authors.

Received 19 January 2009; received in revised form 15 May 2009; accepted 21 May 2009. published online 02 December 2009.

Summary

Mucinous nonneoplastic cyst of the pancreas is a newly described and rare cystic lesion with unknown histogenesis. It is defined as a cystic lesion lined with mucinous epithelium, supported by hypocellular stroma and not communicating with the pancreatic ducts. It is very challenging to differentiate this lesion from other cystic mucinous neoplasms of the pancreas such as branch-duct intraductal papillary mucinous neoplasm by morphology. In this study, a total of 436 pancreatic specimens resected between 2002 and 2007 in our institution were reviewed. Fifteen (3.4%, 15/436) mucinous nonneoplastic cysts were identified. They included 3 males and 12 females, with a median age of 60 years. Forty-six percent of cases (7/15) occurred in pancreatic head, 27% (4/15) in neck, 7% (1/15) in body, and 20% (3/15) in tail. The size of lesions ranged from 0.5 to 3.5 cm in greatest dimension. In most cases (12/15, 80%), mucinous nonneoplastic cyst was associated or adjacent to acinar-ductal mucinous metaplasia. These morphologic data indicate that mucinous nonneoplastic cyst is not really a rare disease and may originate from acinar-duct mucinous metaplasia histogenestically. Furthermore, apomucin immunostains of mucinous nonneoplastic cyst showed MUC1 expressed in 27% (4/15) cases, MUC5AC in 67% (10/15 cases), and MUC2 was were negative in all cases, whereas intraductal papillary mucinous neoplasm (n = 17; 5 main duct type, 12 branch-duct type) showed focal and weak MUC1 positivity in 18% (3/17) cases, MUC2 positivity in 71% (12/17) cases, and all intraductal papillary mucinous neoplasm (17/17) were MUC5AC positive. The clonality assay with the HUMARA gene revealed that the mucinous nonneoplastic cysts were of polyclonal origin. For the first time, using HUMARA assay, we demonstrate the nonneoplastic nature of these cysts and further characterize morphologic and immunophenotypic properties that allow differentiation from intraductal papillary mucinous neooplasm.

Keywords: Mucinous nonneoplastic cyst, Mucin phenotype, Clonality, IPMN