Neuroendocrine Tumors of Pancreas

PNETs Overview - Pancreas's Secret Agents

• Pancreatic Neuroendocrine Tumors (PNETs) arise from pancreatic islet cells.
• Constitute 1-2% of all pancreatic neoplasms; incidence is ↑.
• Classified by WHO (2019) based on Ki-67 index & mitotic count:
  • G1: Ki-67 <3%, mitoses <2/10 HPF
  • G2: Ki-67 3-20%, mitoses 2-20/10 HPF
  • G3: Ki-67 >20%, mitoses >20/10 HPF
  • Neuroendocrine Carcinoma (NEC): Poorly differentiated, G3 morphology.
• Genetic Syndromes Association:
  • MEN1 (most common, ~40% of PNETs)
  • Von Hippel-Lindau (VHL)
  • Neurofibromatosis type 1 (NF1)
  • Tuberous Sclerosis (TSC)

⭐ Most PNETs are non-functional (~60-90%) and often present with mass effects or are found incidentally. Functional tumors present with symptoms related to hormone hypersecretion (e.g., insulinoma, gastrinoma).

Functional PNETs - Hormone Hijackers

Secrete active hormones, causing distinct syndromes.

• Insulinoma:
  • Most common. Whipple's triad (hypoglycemia < 50 mg/dL, neuroglycopenic symptoms, glucose relief).
  • Dx: ↑Insulin, ↑C-peptide with hypoglycemia (72hr fast).
  • Rx: Surgery. Diazoxide/Octreotide if unresectable.
• Gastrinoma (ZES):
  • ↑Gastrin → Peptic ulcers (multiple, distal, refractory), diarrhea.
  • Dx: Fasting gastrin > 1000 pg/mL + gastric pH < 2. Secretin test.
  • Rx: PPIs, surgery.
• VIPoma (Verner-Morrison):
  • WDHA syndrome: Watery Diarrhea, Hypokalemia, Achlorhydria.
  • Dx: ↑VIP > 75 pg/mL.
  • Rx: Fluids, octreotide, surgery.
• Glucagonoma:
  • 4 D's: Dermatitis (Necrolytic Migratory Erythema - NME), Diabetes, DVT, Depression.
  • Dx: ↑Glucagon > 500 pg/mL.
  • Rx: Octreotide, surgery.

⭐ Insulinomas are mostly benign (~90%); others (gastrinoma, VIPoma, glucagonoma) often malignant (>50%).

Diagnosis & Localization - Tumor Detectives

• Biochemical Markers:
  • Chromogranin A (CgA): Most common, ↑ in 60-80%. Non-specific.
  • Specific Hormones (Insulin, Gastrin, etc.): For functional tumors.
  • Pancreatic Polypeptide (PP), Neuron-Specific Enolase (NSE).
• Imaging Arsenal:
  • Anatomical:
    • Multiphasic CT/MRI: Initial localization; arterial hyperenhancement (PNETs are vascular).
    • EUS: Highest sensitivity for small tumors (<2 cm); enables FNA.
  • Functional (SSTR-based):
    • ⁶⁸Ga-DOTATATE PET/CT: Gold standard for well-differentiated PNETs.
    • FDG-PET: For poorly-differentiated/aggressive tumors.
• Pathology:
  • EUS-FNA: For cytological confirmation & Ki-67 proliferation index (grading).

⭐ ⁶⁸Ga-DOTATATE PET/CT has revolutionized PNET staging due to its high sensitivity for SSTR-expressing tumors.

Management & Prognosis - The Treatment Blueprint

• Surgical Resection (Localized Disease): Curative intent.
  • Enucleation (small, <2 cm, low grade).
  • Pancreaticoduodenectomy (head), Distal pancreatectomy (body/tail).
• Unresectable/Metastatic Disease:
  • Somatostatin Analogs (SSAs): Octreotide, Lanreotide (antiproliferative, symptom control).
  • Peptide Receptor Radionuclide Therapy (PRRT): $^{177}$Lu-DOTATATE (SSTR+).
  • Targeted: Everolimus (mTORi), Sunitinib (VEGFRi).
  • Chemotherapy: Streptozocin, Temozolomide (G3/progressive G2).
• Prognosis:
  • Key Factors: WHO Grade (Ki-67: G1 <3%, G2 3-20%, G3 >20%), TNM stage, resectability.
  • Functional tumors: Symptom control is crucial (e.g., SSAs for carcinoid syndrome).

⭐ For unresectable/metastatic well-differentiated (G1/G2) PNETs, Everolimus and Sunitinib are key targeted therapies improving progression-free survival.

High‑Yield Points - ⚡ Biggest Takeaways

• Insulinoma: most common functional PNET; causes hypoglycemia (Whipple's triad).
• Non-functional tumors: most common PNET overall; often large, present with mass effects.
• Strong association with MEN 1 syndrome (Parathyroid, Pancreas, Pituitary glands).
• Gastrinoma (ZES): multiple refractory ulcers, severe diarrhea; secretin stimulation test.
• Glucagonoma: classic necrolytic migratory erythema (NME), diabetes, DVT, depression.
• VIPoma: profuse WDHA syndrome (Watery Diarrhea, Hypokalemia, Achlorhydria).
• Surgical resection is curative for localized tumors; Chromogranin A is key diagnostic marker.