Intraductal papillary mucinous tumour

Intraductal papillary mucinous tumour, abbreviated IPMT, is an uncommon tumour of the pancreas.

It is also known as intraductal papillary mucinous neoplasm (abbreviated IPMN).

General

• Morphologically and biologically distinct from ductal adenocarcinoma, mucinous cystic tumour and ductal papillary hyperplasia.
• Prognosis:
  • Favourable if caught early; not much different than ductal adenocarcinoma if caught late.
  • Dependent what is involved:
    • Main duct (bad prognosis).
    • Branch (good prognosis).

Clinical:

• Patient usually not jaundiced... as no obstruction.
• Often diabetes... as pancreas is destroyed.
• Patients may get a total pancreatectomy - as the disease is often multifocal.

Epidemiology

• ~1% of all exocrine pancreatic tumours.
• More common in males.
• Mean age at presentation 62 years.
• 60-80% occur in the head of the pancreas.
• Average size 4 cm.

Classification of IMPT

Commonly classified by the duct involvement:

1. Main duct type.
   • Commonly associated with invasive carcinoma.
2. Branch duct type.
   • Less commonly associated with invasive carcinoma.

The oncocytic subtype of IPMT is now known to be genetically separate from other types.

Behaviour

• Adenoma.
• Borderline mucinous tumour.
• Carcinoma.

Notes:

• Borderline tumours are rare.
• If intralobular dilated ducts... carcinoma.
• Any margin with mucin cells in thought to be badness!

Gross

• May be patchy/multifocal.
• Multiple cystic spaces.

Microscopic

Features:

• Pancreatic duct lining cells jut into the duct lumen - papillomatous growth pattern.
• Cytology:
  • Cell enlargement.
    • Increased mucin production.
  • Nuclear changes:
    • Increased NC ratio.
    • Nuclear crowding and pleomorphism.
  • Mitotic activity.

Note:

• No ovarian type stroma underneath (as seen in mucinous tumours).

DDx:

• PanIN.
• Invasive ductal carcinoma of the pancreas.
• Intra-ampullary papillary-tubular neoplasm -- see ampulla of Vater.

See also

• Pancreas.