## Distinguishing PDAC from pNET ### Clinical Presentation Differences **Key Point:** Pancreatic neuroendocrine tumours (pNETs) are characterised by elevated neuroendocrine markers (chromogranin A, chromogranin B, neuron-specific enolase [NSE], synaptophysin), whereas PDAC shows minimal elevation of these markers. ### Comparison Table | Feature | PDAC | pNET | |---------|------|------| | **Chromogranin A** | Normal or mildly elevated | Markedly elevated (>90% cases) | | **NSE** | Normal or mildly elevated | Markedly elevated | | **Presentation** | Painless jaundice, abdominal pain | Hormonal syndromes (insulinoma, gastrinoma) | | **Clinical course** | Rapid deterioration, cachexia | Often indolent, slow growth | | **Imaging pattern** | Solid, hypoattenuating, ductal dilation | Solid or cystic, well-circumscribed | | **Prognosis** | Median OS ~12 months (stage IV) | Much better (5-year survival 60–70% for low-grade) | ### Why Neuroendocrine Markers Distinguish Them 1. **pNETs are neuroendocrine tumours** — they arise from neuroendocrine cells and express neuroendocrine granules containing chromogranin and synaptophysin. 2. **PDAC is adenocarcinoma** — it arises from ductal epithelium and does not express neuroendocrine markers at high levels. 3. **Immunohistochemistry** — chromogranin A and synaptophysin staining is positive in >90% of pNETs but negative or weak in PDAC. **High-Yield:** Elevated chromogranin A (>100 ng/mL) is the most sensitive single marker for pNET diagnosis and is rarely markedly elevated in PDAC. **Clinical Pearl:** A patient with a pancreatic mass and dramatically elevated chromogranin A should raise suspicion for pNET rather than PDAC, even if imaging is non-specific. ### Why Other Options Are Less Discriminating - **Painless jaundice** occurs in both PDAC (head of pancreas tumours compressing CBD) and pNETs (if large enough to obstruct ducts). - **Rapid deterioration with cachexia** is typical of PDAC but can occur in advanced pNETs. - **Cystic appearance** is more common in pNETs but PDAC can also present with cystic degeneration.
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