Pancreas

The pancreas hangs-out in the upper abdomen. It occasionally is afflicited by cancers, the most common of which is very fatal.

Normal anatomy

Divided into three portions: head, body & tail:

• Head:
  • Includes unicate process.
  • Extend to superior mesenteric vein (by definition).
• Body:
  • Superior mesenteric vein to left edge of aorta (by definition).
• Tail:
  • Remainder of pancreas.

Pancreatic surgeries

Common pancreatic surgeries include:

• Whipple (includes duodenum).
• Distal pancreatectomy.
  • Removal of tail +/- body.
• Total pancreatectomy.
  • Often with splenectomy.

General classification of pancreatic tumours

• Metstatses.
  • Most common = renal cell carcinoma.
• Primary.
  • Endocrine.
    • Usually small as hormonally active.
  • Exocrine.

Most important cystic lesions

• Serous.
• Mucinous.
  • Ovarian-like stroma.
• Solid pseudopapillay tumours.
• Intraductal papillary mucinous tumour (IPMT).
  • No ovarian-like stroma.

Mnemonic SIMS: Serous, IPMT, Mucinous, Solid pseudopapillary tumour.

Mucinous vs. IMPT

IMPT:

• No ovarian-like stroma.
• Usually has total pancreatectomy.

Cystic tumors of pancreas

• Uncommon.
  • 10% of cystic lesion (90% pseudocyst).
• Diagnostic difficulties (hard to differentiate pseudocyst & cyst).

Note:

• Pseudocysts: not real cysts... as no lining epithelium.

Cystic tumours

General

• 50% incidental finding.
• Vague Sx.
• Abdo mass.
• Wt loss.
• Jaundice.

Note:

• Usually diagnosed by imaging (CT/MRI, ERCP, Endoscopic ultrasound).

Serous cystic tumours

General=

• Cell of origin: intralobular duct cells (ductular cells).
• Glycogen rich - but do not produce mucin.

Subclassication

• Serous microcystic adenoma.
  • Many small cysts.
• Serous oligocystic adenoma.
  • Large cysts.
• Serous adenocarcinoma - rare.

Note:

• If one mucin +ve cell, tumour = a mucinous tumour.

Characteristics of serous microcystic adenoma

• 1-2% of all exocrine pancratic tumours.
• Female>Male.
• Mean age 66 years.
• Truly benign with no malignant potenial.
• May not require surgical resection.
• May be part of von Hippel-Lindau.
• 50-70% occur in the body and tail.
• Average size 11 cm.

Radiology

• Honey comb appearance.
• "Coin lesion" - well demarcated border.
• May have central scar.

Gross

• Bosulated surface.
  • Lobulated.
• No (macroscopic) cysts apparent on gross.

Microscopic

Features:

• Cuboidal cells.
  • Glycogen rich.

DDx

• Renal cell carcinoma.
• Lympangioma.
• Hemangiomas.
• Oligocystic - mucinous cystic tumors and pseudocysts.
  • Have mucinous -- PAS-D could be used.
• Serous adenoma my coexist with aggressive tumours.

Mucinous cystic tumours

• Gastro-entero-pancreatic cell differentiation with hypercellular ovarian-type stroma.
  • Stroma --> cellular.
• 2-2.5% of all exocrine pancreatic tumours.
• Almost exclusively in women.
• Mean age - 49 years.
• >80% in body and tail.
• Average size ~10 cm.

Note:

• Looks different than serous tumour.

Subclassification

• Sucinous cystadenoma.
• Borderline mucinous cystic tumour.
• Mucinous cystadenocarcinoma.

Borderline vs. Carcinoma

• Few mitoses in borderline.

Radiology

• Mucinous tumours: multilocular.
• Generally larger than serous.
• Often partially solid and cystic.
• Often calcified.
  • Calcification rare in serous.
• Usually tail & body.

Microscopic

Mucinous cystadenoma

Features:

• Simple tall columnar epithelium with large mucin vacuole on apical aspect.
• "Ovarian-type stroma" under epithelium.
  • Ovarin-type stroma: high density of small (non-wavy) spindle cells with eosinophilic cytoplasm.

Image: Mucinous cystadenoma - ovary (uchc.edu).

Notes:

• Appearance similar to mucinous cystadenoma in the ovary.
• Mucin stains +ve (intracytoplasmic).

Borderline mucinous cystic tumour

Features:

• May have finger like projections.
• Pseudostratification of epithelium.

Notes:

• Surgery does not change based on diagnosis on frozen section.
  • Only question is "Is the margin clear?".
• Borderline tumours are rare.

Carcinoma

• Cells floating in mucin.

Mucinous tumour vs. pseudocyst

mucinous t pseudocyst amylase & lipase low high viscosity high low CEA, CA124 high low

Prognosis:

• Benign looking tumours have the potential to transform into carcinoma.
• No report of assoc. pseudomyxoma peritonei.
  • US boards question -- it is an exception ... others one cause it.
• Prognosis of m. cystadenocarcinoma is slightly better than that of ductal adenocarcinoma.

IPMT

Intraductal papillary mucinous tumour (IPMT)

• Papillomatous growth pattern.
• Morphologically and biologically distinct from ductal adenocarcinoma, mucinous cystic tumour and ductal papillary hyperplasia.
• 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

Khalifa's theory:

• Nothing but dilation of pancreatic duct + hypersecretion.

Gross

• May be patchy/multifocal.

Sequence

• Hyperplasia.
• Adenomatous hyperplasia.
• Carcinoma in situ.
• Invasive carcinoma.

K-ras oncogene muation associated - seen in all stages of the sequence.

Characteristics

• Cell enlargement.
• Incr. NC ratio.
• Nuclear crowding and pleomorphism.
• Papillary tufting.
• Mitotic activity.
• Increased mucin production.

classification IMPT

• Adenoma.
• Borderline mucinous tumour.
• Carcinoma.

NB1

• No ovarian like stroma.
• In duct.

NB2

• Usually not jaundiced... as no obstruction.
• Often diabetes... as pancreas is destroyed.

Gross

• Multiple cystic spaces.

Micro

• Some places -- fronds of benign looking mucin producing epithelium.
• No ovarian type stroma underneath.

NB

• If no viable cells in the mucin then not cancer.
  • Mucin under pressure can disect through the tissue.
• Borderline tumours are rare.

Pitfalls

• Since it is multifocal may involve large segment of the ductal system.
  • Patients often get a total pancreatectomy.
  • If intralobular dilated ducts... carcinoma.
• Hard to get a negative margin.

Prognosis: favourable.

NB - any margin with mucin cells -- badness!!!

• Dilated = mucin producing ducts (???).
  • DDx: PAN-IN1.
    • Needs a totally pancreatectomy.

Solid pseudopapillary tumour

General

• Obscure cell of origin.
• Considered low grade, i.e. prognosis is usually good.

Epidemiology

Features:

• Usually females (M:F=1:9).
• Mean age of presentation third decade (20s).

Management

May be followed radiologically.

Microscopic

Features:

• Solid sheets of cells, focally dyscohesive.
• Eosinophilic cytoplasm.
  • Occasionally clear cytoplasm.
  • Focal eosinophilic (intracytoplasmic) globules - key feature.
• Uniform nuclei with occasional nuclear grooves.
• +/-Necrosis - creating spaces/cavities.

Image: Solid pseudopapillary tumour (bmj.com).

DDx

• Pseudocyst.
• Cystadenoma.
• Cystadenocarcinoma.

Carcinomas

• Usually head of pancreas.

DDx:

• Mucinous tumour (may be misdiagnosed as this).
• Serous tumour (microcystic).

Gross

• Necrosis.
• Capsule.
• Hemorrhage.

Microscopic

Features:

• Solid.
• Necrosis.
  • Myxoid degeneration.
• Cells around vessels.
• Nuclei.
  • Bland.
  • Small nuclei.
  • Little pleomorphism.
  • Sometimes coffee-bean appearance.
• Cytoplasm - granular, abundant.
• Quasi endocrine look.
  • May stain positive for endocrine markers.

Cystic tumours

• Diagnosed by imaging/with help of images.

Stains

• PAS-D

Prognosis: very favourable (mostly benign).

Cystic tumours of the pancreas

	Sex	Age (years)	Usual site	Typical size (cm)
Microcystic	female	66	B&T	11
Mucinous	female	49	B&T	10
IPMT	male	62	H	4
Pseudopapillary	female	35	any	7.5

External links

• Pancreatic cancer - PanINs - pancreaticcancer2000.com.