## Gleason Grading System for Prostate Cancer **Key Point:** The Gleason score is the sum of the primary (most common) grade and the secondary (second most common) grade in the tumor specimen. This is the gold standard for prostate cancer grading and prognostication. ### Gleason Grade Scale | Grade | Histological Features | Differentiation | | --- | --- | --- | | 1 | Well-formed glands, minimal nuclear atypia | Well-differentiated | | 2 | Well-formed glands with slight variation, minimal stromal invasion | Well-differentiated | | 3 | Individual glands, infiltrative pattern, moderate atypia | Moderately differentiated | | 4 | Fused glands, cribriform pattern, marked atypia | Poorly differentiated | | 5 | No glandular differentiation, solid sheets, marked nuclear atypia | Undifferentiated | ### Gleason Score Interpretation **High-Yield:** Gleason score ranges from 2 to 10 (primary grade 1–5 + secondary grade 1–5). Modern practice uses a 5-tier prognostic grouping: - **Group 1:** Gleason ≤6 (low risk) - **Group 2:** Gleason 3+4=7 (intermediate risk, favorable) - **Group 3:** Gleason 4+3=7 (intermediate risk, unfavorable) - **Group 4:** Gleason 8 (high risk) - **Group 5:** Gleason 9–10 (very high risk) **Mnemonic:** **PPH** = Primary + Primary + Higher secondary. The primary grade appears twice because it dominates the tumor architecture; the secondary grade (second most common) is added once. **Clinical Pearl:** A Gleason score of 4+3=7 has worse prognosis than 3+4=7 because the higher-grade (grade 4) component is more extensive. This distinction is critical for treatment planning. **Warning:** Do not confuse Gleason score with PSA level or TNM stage — all three are independent prognostic factors and must be considered together in risk stratification.
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