Small intestine & ampulla
Ampulla
Intra-ampullary papillary tubular neoplasm (IAPN)

Deputy Editor-in-Chief: Raul S. Gonzalez, M.D.
Felicia D. Allard, M.D.

Topic Completed: 6 July 2020

Minor changes: 6 July 2020

Copyright: 2003-2020, PathologyOutlines.com, Inc.

PubMed Search: IAPN

Felicia D. Allard, M.D.
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Cite this page: Allard FD. Intra-ampullary papillary tubular neoplasm (IAPN). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/ampullaiapn.html. Accessed August 6th, 2020.
Definition / general
  • Intra-ampullary papillary tubular neoplasm (IAPN) is the name proposed in 2010 to unify the nomenclature for mass forming preinvasive (dysplastic) lesions that arise within the ampulla of Vater (Am J Surg Pathol 2010;34:1731)
Essential features
Terminology
  • Other / previous terms include intestinal type adenoma, noninvasive pancreatobiliary type neoplasm
ICD coding
  • ICD-O: 8210/0 - adenomatous polyp, low grade dysplasia
  • ICD-O: 8210/2 - adenomatous polyp, high grade dysplasia
  • ICD-10: C24.1 - malignant neoplasm of ampulla of Vater
  • ICD-11: 2E92.2 & XH3DV3 - benign neoplasm of duodenum, adenoma, NOS
  • ICD-11: 2E92.2 & XH8MU5 - benign neoplasm of duodenum, adenomatous polyp, NOS
Epidemiology
Sites
  • Ampulla of Vater: within the ampullary channel (common channel) or the intra-ampullary portions of the common bile duct or main pancreatic duct
Etiology
  • Given the prevalence of neoplasia in and around the ampulla, authors have speculated that bile acids may be carcinogenic (Mutat Res 2005;589:47)
Clinical features
  • Patients may be asymptomatic or present with obstructive symptoms: jaundice, weight loss, abdominal pain, nausea / vomiting, pruritus, dark urine / light stools or tarry stools (Am J Surg Pathol 2010;34:1731)
  • Rarely, patients present with cholangitis or pancreatitis
Diagnosis
  • A mass involving the ampullary region may be found on cross sectional imaging
  • Tissue diagnosis is often made via endoscopic retrograde cholangiopancreatography (ERCP) biopsy
Radiology description
  • Imaging modalities used to examine the ampulla include computed tomography (CT) and magnetic resonance imaging (MRI) (Am J Surg Pathol 2010;34:1731)
  • Imaging generally shows a dilated common bile duct, intra / extrahepatic ducts; an ampullary, duodenal or pancreatic mass; or enlarged or irregular papillae (Am J Surg Pathol 2010;34:1731)
Prognostic factors
Treatment
Gross description
Gross images

Images hosted on other servers:

IAPN gross / histologic correlation

Microscopic (histologic) description
  • Noninvasive exophytic tumor
  • Growth pattern often shows a mixture of papillary and tubular architecture (Am J Surg Pathol 2010;34:1731)
  • In one large series, cases showing predominantly papillary architecture were more likely to contain high grade dysplasia (Am J Surg Pathol 2010;34:1731)
  • When considering the predominant phenotype, the majority show an intestinal phenotype, with a minority showing a gastric / pancreatobiliary phenotype (74% versus 26%, respectively) (Am J Surg Pathol 2010;34:1731, Hum Pathol 2014;45:1910)
    • Intestinal type: tall columnar cells with elongated nuclei and inconspicuous nucleoli; Paneth, goblet or endocrine cells may be present; appear similar to conventional colonic adenomas
    • Pancreatobiliary type: cuboidal cells with round nuclei arranged predominantly in a single layer; some resemble a pyloric gland adenoma histologically
  • When taking into account all morphology present, 45% of cases show a mixed phenotype (Am J Surg Pathol 2010;34:1731)
  • Many to most do not show significant mucin production (Ann Surg 2016;263:162, Am J Surg Pathol 2010;34:1731)
  • At least focal high grade dysplasia is present in most cases (66.7 - 94%) (Am J Surg Pathol 2010;34:1731, Hum Pathol 2014;45:1910)
    • Increased degree of architectural complexity and nuclear atypia
  • Lesions with a pancreatobiliary phenotype are more likely to have more extensive high grade dysplasia (Am J Surg Pathol 2010;34:1731)
Microscopic (histologic) images

Contributed by Felicia D. Allard, M.D.

Pancreatobiliary type IAPN

Intestinal type IAPN

Paneth and goblet cells

Intestinal IAPN with high grade dysplasia

Pancreaticobiliary phenotype tubular growth



Images hosted on other servers:

IAPN phenotype immune profiles

Cytology description
  • The majority of IAPNs are accessible to endoscopic biopsy; however, exfoliative cytology is sometimes done and can be used to diagnose dysplasia (Cytojournal 2017;14:19)
Positive stains
Negative stains
Sample pathology report
  • Ampulla, endoscopic ampullectomy:
    • Intra-ampullary papillary tubular neoplasm, pancreatobiliary type, with multifocal high grade dysplasia
    • No invasive carcinoma identified
    • Resection margins are free of dysplasia
Differential diagnosis
  • Intraductal papillary mucinous neoplasm (IPMN):
    • These lesions arise in the pancreatic ducts (main duct or side branch ducts) and generally have significant mucin production
    • Proper grossing and sampling with specific location information of the tissue sampled are crucial in making the distinction between these entities, because without knowledge of the specific location of a given lesion, these can be histologically indistinguishable at microscopic level
  • Duodenal / periampullary adenoma:
    • These lesions will generally show an intestinal phenotype (will look like a colonic adenoma)
    • Proper grossing and sampling with specific location information of the tissue sampled are crucial in making the distinction between these entities, because without knowledge of the specific location of a given lesion, these can be histologically indistinguishable at microscopic level
  • Intra-ampullary adenocarcinoma:
    • This is an adenocarcinoma that may arise from an IAPN but will show an invasive component
Board review style question #1

A 65 year old man presented with jaundice, weight loss and nausea. MRI showed a dilation of the intra and extrahepatic bile ducts with an ill defined fullness in the head of the pancreas; ERCP revealed a papillary mass in the ampullary channel. Forcep biopsy demonstrates histologic findings consistent with intra-ampullary papillary tubular neoplasm (IAPN) with high grade dysplasia including the pictured findings. The most likely immunoprofile for this lesion is

  1. Immunoreactive for CDX2, CK20 and MUC2; negative for MUC1 and MUC5AC
  2. Immunoreactive for CDX2, MUC1 and MUC2; negative for CK20 and MUC5AC
  3. Immunoreactive for MUC1 and MUC5AC; negative for CDX2, CK20 and MUC2
  4. Immunoreactive for MUC1, MUC2 and MUC5AC; negative for CDX2, CK20 and CK7
Board review answer #1
A. Immunoreactive for CDX2, CK20 and MUC2; negative for MUC1 and MUC5AC. The question discusses a typical clinical presentation for a patient who has an intra-ampullary papillary tubular neoplasm (IAPN). The histologic image demonstrates neoplastic epithelium composed of columnar cells with elongated, hyperchromatic nuclei. Paneth cells and goblet cells are present. These findings support an intestinal phenotype; answer A contains the most common immunoprofile for an intestinal type IAPN. Answer choice C is the most common immunophenotype for a pancreatobiliary type IAPN.

Comment Here

Reference: Intra-ampullary papillary tubular neoplasm (IAPN)
Board review style question #2
A 65 year old man presented for evaluation of abdominal pain and weight loss. His wife noted that his skin and eyes were becoming yellow. Imaging revealed dilation of the main pancreatic duct and common bile duct. ERCP showed an exophytic mass filling the common channel of the ampulla; a biopsy was obtained for evaluation. Histology most likely showed a lesion comprised of which type of epithelium?

  1. Intestinal
  2. Oncocytic
  3. Pancreatobiliary
  4. Squamous
Board review answer #2
C. Pancreatobiliary. The lesion described above is most likely an intra-ampullary papillary tubular neoplasm (IAPN). The majority (74%, in one large study) show a predominantly gastric / pancreatobiliary phenotype. The other epithelial phenotype described with IAPN is intestinal; IAPNs may in many cases show a mixture of the 2 epithelial types. Oncocytic and squamous epithelial types are not seen in IAPNs.

Comment Here

Reference: Intra-ampullary papillary tubular neoplasm (IAPN)
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