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"pancreatic cancer" AND pathogenesis

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I now have everything needed. Here is the full explanation of PA 31.7 - Pancreatic Cancer:

PA 31.7 - Pancreatic Cancer

Etiology, Pathogenesis, Manifestations, Laboratory, Morphology, Complications & Metastases

1. Overview & Epidemiology

Pancreatic cancer refers predominantly to infiltrating ductal adenocarcinoma, the most common exocrine malignancy of the pancreas. It is the 3rd leading cause of cancer death in the United States (behind lung and colon). Despite being less common than those two, it has one of the highest mortality rates of any cancer - 5-year survival is approximately 12%, largely because >80% of patients present with surgically unresectable disease.

~64,000 Americans diagnosed per year
80% of cases occur between ages 60-80
Mean time from diagnosis to death is often just months

2. Etiology (Risk Factors)

Risk Factor	Notes
Smoking	Strongest environmental risk - doubles the risk
Chronic pancreatitis	Both risk factor AND possible manifestation of the cancer
Long-standing diabetes	Increased risk; new-onset diabetes in older adults can be the first sign
Age	80% of cases between 60-80 years
Familial/Genetic	Germline BRCA2 mutations (~10%), mismatch repair gene mutations, PALB2, ATM, CDKN2A
Obesity	Modestly elevated risk

Note: Chronic pancreatitis and diabetes can be caused by pancreatic cancer too (e.g., a head-of-pancreas tumor obstructs the duct, causing pancreatitis in the distal pancreas). About 1% of older adults with new-onset diabetes harbor unsuspected pancreatic cancer.

3. Pathogenesis

Pancreatic cancer arises from a stepwise accumulation of mutations through Pancreatic Intraepithelial Neoplasia (PanIN) - microscopic precursor lesions in small ducts. >85% of pancreatic cancers arise from PanIN.

The progression model:

PanIN to Invasive Carcinoma progression model showing stepwise genetic changes from healthy duct through PanIN-1A, PanIN-1B, PanIN-2, PanIN-3 to invasive carcinoma

PanIN progression model - Robbins & Kumar Basic Pathology

Key Molecular Alterations (in order of acquisition):

Early (PanIN-1):

Telomere shortening - allows chromosomal instability
KRAS mutation (chr 12p) - present in >90% of pancreatic cancers. Activating point mutation impairs GTPase activity, leaving KRAS constitutively active. This drives uncontrolled proliferation via the MAPK and PI3K pathways.

Intermediate (PanIN-2):

CDKN2A/p16 inactivation (chr 9p) - present in ~30%. Encodes two suppressors: p16/INK4a (blocks CDK4, halts cell cycle at G1) and ARF (stabilizes p53). Inactivated by point mutations or homozygous deletion.

Late (PanIN-3 / high-grade):

TP53 inactivation (chr 17p) - present in 70-75%. Removes the key checkpoint for DNA damage response, apoptosis, and senescence.
SMAD4 inactivation (chr 18q) - present in 55%. Highly specific to pancreatic cancer. SMAD4 mediates TGF-β tumor suppression signaling. Its loss is near-unique to pancreatic cancer among all solid tumors.
BRCA2 - mutated late in a subset of cases (both germline and somatic)

Summary table of key mutations:

Gene	Chr	Frequency	Function
KRAS	12p	>90%	GTPase signal transducer (oncogene)
TP53	17p	70-75%	DNA damage response, apoptosis
SMAD4	18q	55%	TGF-β tumor suppressor
CDKN2A/p16	9p	~30%	Cell cycle brake (G1/S checkpoint)

4. Morphologic Features

Gross (Macroscopic):

60% arise in the head of the pancreas; 15% in the body; 5% in the tail; 20% diffuse
Hard, gray-white, stellate, poorly defined mass
Highly invasive even at early stages
Head-of-pancreas tumors typically obstruct the common bile duct → biliary dilation, jaundice

Microscopic (Histology):

Histology of pancreatic carcinoma showing moderately to poorly formed glands with malignant epithelial cells in densely fibrotic desmoplastic stroma

Fig: (A) Gross white mass centered on the pancreatic duct. (B) Moderately to poorly formed malignant glands within densely fibrotic stroma, with perineural invasion - Robbins, Cotran & Kumar

Higher magnification histology showing abortive gland formation with mucin secretion and aggressive infiltrative growth in desmoplastic stroma

Fig: Poorly formed glands in a densely desmoplastic stroma - Robbins & Kumar Basic Pathology

Key histological features:

Moderately to poorly differentiated adenocarcinoma
Abortive gland formation with mucin secretion
Dense desmoplastic stroma (intense host fibrotic reaction) - this stromal reaction is a hallmark
Perineural invasion - classic and important (accounts for pain)
Lymphovascular invasion - commonly seen
Aggressive, deeply infiltrative growth pattern even in "early" lesions

5. Clinical Manifestations

Pancreatic cancer remains silent until it obstructs or invades adjacent structures. This is why most patients present late.

Symptom	Mechanism	Notes
Abdominal/back pain	Perineural invasion, retroperitoneal involvement	Usually the first symptom; by this point, often unresectable
Obstructive jaundice	Common bile duct obstruction by head lesion	Painless jaundice is classic for head of pancreas
Courvoisier sign	CBD obstruction → gallbladder distension	Palpably enlarged, non-tender gallbladder + painless jaundice
New-onset diabetes	Islet cell destruction, duct obstruction causing pancreatitis	Can be the first clue in ~1% of older adults
Weight loss, anorexia, malaise	Advanced disease, cancer cachexia	Profound loss of skeletal muscle and visceral fat
Migratory thrombophlebitis (Trousseau sign)	Tumor secretes procoagulants and platelet-aggregating factors	Occurs in ~10% of patients

6. Laboratory Features

Test	Finding	Clinical Significance
CA 19-9	Elevated	Most commonly used tumor marker; NOT sensitive or specific enough for screening, but useful for monitoring treatment response
CEA	Elevated	Similarly not specific enough for screening
Circulating tumor DNA (ctDNA)	Often elevated	Useful for treatment monitoring but lacks sensitivity for early detection
Liver function tests	Elevated bilirubin, ALP (obstructive pattern)	With biliary obstruction
Blood glucose	Elevated	New-onset diabetes
Amylase/Lipase	May be elevated if duct obstruction causes pancreatitis

USPSTF does not recommend screening the general population due to poor sensitivity/specificity of available tests. Surveillance is recommended only for high-risk individuals with germline mutations (BRCA2, PALB2, ATM, Lynch syndrome).

Imaging:

Endoscopic ultrasound (EUS) - best for small lesions and tissue sampling
CT scan (pancreatic protocol) - standard for staging; assesses resectability
ERCP / MRCP - evaluates biliary/pancreatic duct involvement

7. Complications

Complication	Mechanism
Biliary obstruction	Tumor in pancreatic head compresses common bile duct
Duodenal obstruction	Tumor invades or compresses the duodenum
Malabsorption/steatorrhea	Pancreatic duct obstruction → exocrine insufficiency
Diabetes mellitus	Islet cell destruction or duct obstruction-induced pancreatitis
Migratory thrombophlebitis	Hypercoagulable state (Trousseau syndrome)
Cancer cachexia	Profound wasting, systemic cytokines
Chronic pain	Perineural invasion and celiac plexus involvement
Gastric varices/portal hypertension	If splenic or portal vein is invaded

8. Metastases

Pancreatic cancer metastasizes early and widely. The pattern follows:

Local/Regional spread (most common and earliest):

Retroperitoneal invasion (wraps around vessels and nerves)
Peripancreatic lymph nodes → gastric, mesenteric, omental, portahepatic nodes
Direct invasion of: spleen, adrenal glands, transverse colon, stomach, vertebral column
Encasement of major vessels (SMA, celiac trunk, portal vein) = unresectable

Distant metastases:

Liver - most common distant site; liver is often massively enlarged with metastatic deposits
Lungs
Bones (less common)
Peritoneal seeding (carcinomatosis)

The high rate of unresectability (>80% at diagnosis) is driven by both local vascular invasion and distant metastases - most commonly to the liver.

Key Concepts Summary

Most common type: Infiltrating ductal adenocarcinoma
Location: 60% in the head
Key precursor lesion: PanIN (pancreatic intraepithelial neoplasia)
Most common mutation: KRAS (>90%)
Hallmark histology: Desmoplastic stroma + poorly formed glands + perineural invasion
Classic presentation: Painless jaundice (head lesion) OR pain (late finding)
Trousseau sign: Migratory thrombophlebitis in 10%
Best tumor marker: CA 19-9 (for monitoring, not screening)
5-year survival: ~12% (dismal due to late presentation)
Most common metastatic site: Liver

Sources: Robbins, Cotran & Kumar - Pathologic Basis of Disease; Robbins & Kumar - Basic Pathology

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Pancreatic Neuroendocrine Neoplasms complete infographic

Here is everything from the second image - Pancreatic Neuroendocrine Neoplasms (PanNENs) - in one picture. Here is a quick read-through of the key points:

General PanNENs - Only 2% of pancreatic tumors; graded by Ki-67; mutations in MEN1, PTEN/TSC2, ATRX/DAXX.

Insulinoma (β-cell) - Most common PanNEN. Excess insulin → hypoglycemia (BG <50 mg/dL). Classic triad: symptoms with fasting, low glucose, relief with eating. 90% benign. Amyloid deposits on histology. Treat with surgical excision.

Gastrinoma / ZES (G-cell) - Found in the "gastrinoma triangle." Excess gastrin → excess acid → multiple/refractory peptic ulcers, even in the jejunum. 25% part of MEN-1. >50% already malignant at diagnosis. Treat with PPIs + surgery.

Rare tumors:

Glucagonoma (α-cell) - necrolytic migratory erythema skin rash + mild DM + anemia
Somatostatinoma (δ-cell) - "3 Ds": Diabetes, Diarrhea (steatorrhea), gallstones (cholelithiasis)
VIPoma - WDHA syndrome (Watery Diarrhea, Hypokalemia, Achlorhydria)
PPoma - asymptomatic mass lesion

Source: Robbins, Cotran & Kumar - Pathologic Basis of Disease

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