## Histological Classification of Prostate Cancer **Key Point:** Adenocarcinoma accounts for >95% of all prostate cancers and is the standard histological type unless otherwise specified. ### Adenocarcinoma Subtypes | Subtype | Frequency | Key Features | | --- | --- | --- | | Acinar (conventional) | ~70% | Most common; arises from acinar epithelium | | Ductal | ~5% | More aggressive; higher Gleason scores | | Mucinous | <1% | Mucin-producing; poor prognosis | | Signet-ring cell | <1% | Rare; aggressive | | Neuroendocrine | <1% | Very aggressive; often hormone-resistant | ### Rare Histological Types - **Squamous cell carcinoma:** <1% of cases; arises from metaplastic squamous epithelium; associated with chronic irritation or prior therapy - **Small cell carcinoma:** <1%; neuroendocrine origin; highly aggressive; often presents with metastatic disease - **Transitional cell carcinoma:** Arises from urothelium at the prostatic urethra; rare; associated with bladder cancer **High-Yield:** On any prostate cancer question, assume adenocarcinoma unless the stem explicitly states otherwise. Grading is by Gleason score (2–10), not TNM staging alone. **Clinical Pearl:** Adenocarcinomas are further classified by growth pattern (acinar, cribriform, solid, etc.) and assigned a primary and secondary Gleason grade; the sum determines the Gleason score.
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