## Histological Classification of Pancreatic Cancer **Key Point:** Ductal adenocarcinoma (PDAC) accounts for approximately 85–90% of all pancreatic malignancies, making it by far the most common type. ### Epidemiology and Incidence | Histological Type | Frequency | 5-Year Survival | Key Features | | --- | --- | --- | --- | | Ductal adenocarcinoma | 85–90% | 5–10% | Highly aggressive, desmoplastic stroma, poor prognosis | | Neuroendocrine tumors | 3–5% | 40–60% | Slower growth, better prognosis if localized | | Acinar cell carcinoma | 1–2% | 20–30% | Low-grade, often presents late | | Mucinous cystic neoplasm | <1% (of malignancies) | Variable | Often cystic, better prognosis if resected early | ### Ductal Adenocarcinoma Characteristics **High-Yield:** PDAC is characterized by: - Aggressive biological behavior with early invasion and metastasis - Dense desmoplastic (fibrotic) stromal reaction - High rates of perineural invasion - Frequent involvement of major vessels at presentation - Mutations in KRAS (90%), TP53 (70%), CDKN2A (95%), and SMAD4 (55%) **Clinical Pearl:** The dense stromal reaction in ductal adenocarcinoma creates a hypoxic microenvironment that limits chemotherapy penetration and contributes to treatment resistance. **Mnemonic: PDAC Bad Prognosis — "KRAS TP53 SMAD4"** — These are the most frequently mutated genes in pancreatic ductal adenocarcinoma, driving its aggressive phenotype. ### Why Other Types Are Less Common - **Neuroendocrine tumors:** Arise from islet cells; much rarer and often have better outcomes - **Acinar cell carcinoma:** Extremely rare; arises from acinar epithelium - **Mucinous cystic neoplasm:** Most are benign or borderline; malignant transformation is uncommon [cite:Robbins 10e Ch 20]
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