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.

Pancreas neoplasms in a table

Type	Key feature	Subtypes	Image	IHC	Detailed microscopic	Usual location	Other	DDx
Serous tumours	cuboidal cells, clear cytoplasm	cystadenoma, borderline t., cystadenocarcinoma	Image?	IHC?	cuboidal cells, clear cytoplasm, central nucleus	body or tail	-	clear cell RCC, oligomucinous mucinous tumours
Intraductal papillary mucinous tumour (IPMT)	mucin, no ovarian-like stroma	clear cell variant	Image?	IHC?	papillae, tall columnar mucin-producing cells	head	-	mucious neoplasms (other pancreatic, duodenal)
Mucinous tumour	mucin, ovarian-like stroma	cystadenoma, borderline t., cystadenocarcinoma	Image?	IHC?	tall columnar mucin-producing cells, ovarian-like stroma	body or tail	-	IPMT, metastatic mucinous tumours
Solid pseudopapillary tumour	eosinophilic intracytoplasmic globules	clear cell variant (cytoplasm clear)	Image?	IHC	sheets of cells, focally loosely cohesive, eosinophilic cytoplasm, uniform nuclei with grooves	none	-	Ductal adenocarcinoma
Ductal adenocarcinoma	irregular shaped glands, cytologic atypia	mucinous, spindle cell, mixed ductal-endocrine	Image?	IHC?	glands, sheets, single cells, nuc. atypia, +/-mitoses, +/-necrosis	head	-	Ampullary carcinoma, chronic pancreatitis
Pancreatoblastoma	squamoid nests, whorling	-	Image?	IHC?	squamoid nests of cells, whorling, nested growth, +/-keratinization	none	-	Ampullary carcinoma, chronic pancreatitis
Acinar cell carcinoma	acinar arch.	-	Image?	IHC?	nests or trabeculae, nucleolus, mod. basophilic granular cytoplasm	head (slight predilection)	-	Ampullary carcinoma, chronic pancreatitis
Undifferentiated carcinoma with osteoclast-like giant cells	giant cells	-	Image?	IHC?	giant cells, usu. with AIS or inv. ductal adenocarcinoma	head	-	Anaplastic carcinoma
Chronic pancreatitis	fibrosis, loss of acinar tissue	-	Image?	IHC?	loss of acinar tissue with preservation of islets, fibrosis	?	-	ductal adenocarcinoma

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 mucin; PAS-D could be used to demonstrate its presence.

Notes:

• 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

Khalifa's table of cystic tumours:

	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.