Pancreas

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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.[1]

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:[2]

  • 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:[3]

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

Management

May be followed radiologically.

Microscopic

Features:[4]

  • Solid sheets of cells, focally dyscohesive.
  • Eosinophilic cytoplasm.
    • Occasionally clear cytoplasm.[5]
    • 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

References

  1. MK. Half-day.
  2. GLP P.489.
  3. GLP P.493.
  4. GLP P.493-5.
  5. Serra S, Chetty R (November 2008). "Revision 2: an immunohistochemical approach and evaluation of solid pseudopapillary tumour of the pancreas". J. Clin. Pathol. 61 (11): 1153–9. doi:10.1136/jcp.2008.057828. PMID 18708424. http://jcp.bmj.com/content/61/11/1153.

External links