Intraductal Oncocytic Papillary Neoplasm of the Pancreas

Definition

• Cystic lesion of the pancreatic ducts containing papillary proliferations of oncocytic cells

Alternate/Historical Names

• Compact cell type intraductal papillary mucinous neoplasm (IPMN)
• IOPN
• Considered by WHO 2010 to be a subtype of IPMN
  • Lack of KRAS mutation suggests an independent entity

Diagnostic Criteria

• Unilocular or multilocular cysts formed by dilated ducts
  • Communication with ducts may be difficult to identify
• Variably complex intraluminal papillary proliferations
  • Usually complex arborizing branching
  • Usually with thin fibrovascular cores
• Lining ranges from simple to stratified to fused solid areas
  • Non-papillary areas lined by flattened or cuboidal epithelium
• Cysts and papillae lined by oncocytic cells
  • Oxyphilic granular cytoplasm
  • Scattered goblet cells frequently seen
• Intracytoplasmic lumens frequent
  • Lumens in solid areas create a cribriform pattern
• Large round uniform nuclei
  • Prominent nucleoli
  • Mitotic figures may be up to 5/hpf
• Paucicellular stroma
  • Frequently hyalinized
• Infrequent findings
  • Psammoma bodies
  • Focal squamous metaplasia
  • Acellular mucin lakes
  • Focal severe cytologic atypia
• Locally invasive carcinoma reported in 2/11 cases
  • Composed of similar cells
  • No cancer related deaths yet reported
• Age range 39-78

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/updates: 1/3/09, 1/2/12

Supplemental studies

Immunohistology

Genetic studies

• IOPN lacks the KRAS mutation frequently found in IPMN

Differential Diagnosis

Mucinous Cystic Neoplasm of the Pancreas	Intraductal Oncocytic Papillary Neoplasm
Lacks oncocytic epithelium	Oncocytic epithelium
Lacks intracytoplasmic lumens and cribriform pattern	Prominent cribriform pattern formed by intracytoplasmic lumens
Complex papillae not seen	Complex arborizing papillae
Cellular ovarian type stroma	Paucicellular stroma
No communication with ducts	Communicates with duct system

Grading/Staging

Grading

• Stratification, nuclear size, prominent nucleoli and frequent mitotic figures would normally justify designation as carcinoma using IPMN criteria
• Limited clinical followup to date has not shown aggressive behavior
Staging
• Staging is not relevant unless invasive carcinoma is present

Lists

Cystic Pancreatic Lesions

• Acinar cell cystadenocarcinoma
• Acinar cell cystadenoma
• Enterogenous duplication cyst
• Epidermoid cyst in intrapancreatic accessory spleen
• Intraductal oncocytic papillary neoplasm
• Intraductal papillary mucinous neoplasm
• Islet cell / well differentiated neuroendocrine tumor (occasionally cystic)
• Lymphangioma
• Lymphoepithelial cyst
• Mucinous cystic neoplasm
• Paraduodenal wall cyst
• Pseudocyst
• Serous cystadenocarcinoma
• Serous oligocystic adenoma
• Serous microcystic adenoma
• Solid and cystic hamartoma
• Solid pseudopapillary neoplasm
• Squamoid cyst of pancreatic ducts
• von Hippel Lindau associated cystic lesions

Bibliography

• Bosman FT, Carneiro F, Hruban RH, Thiese ND (Eds). WHO Classifiication of Tumors of the Digestive System, IARC, Lyon 2010.
• Adsay NV, Adair CF, Heffess CS, Klimstra DS. Intraductal oncocytic papillary neoplasms of the pancreas. Am J Surg Pathol. 1996 Aug;20(8):980-94.
• Patel SA, Adams R, Goldstein M, Moskaluk CA. Genetic analysis of invasive carcinoma arising in intraductal oncocytic papillary neoplasm of the pancreas. Am J Surg Pathol. 2002 Aug;26(8):1071-7.
• Lüttges J, Zamboni G, Longnecker D, Klöppel G. The immunohistochemical mucin expression pattern distinguishes different types of intraductal papillary mucinous neoplasms of the pancreas and determines their relationship to mucinous noncystic carcinoma and ductal adenocarcinoma. Am J Surg Pathol. 2001 Jul;25(7):942-8.
• Basturk O, Coban I, Adsay NV. Pancreatic cysts: pathologic classification, differential diagnosis, and clinical implications. Arch Pathol Lab Med. 2009 Mar;133(3):423-38.