Which histological feature best distinguishes Gleason grade 3 from Gleason grade 4 prostate adenocarcinoma?

Question

Accepted Answer

B. Presence of infiltrative glands with irregular borders and loss of glandular differentiation. ## Gleason Grading System: Grade 3 vs Grade 4

**Key Point:** The Gleason grading system for prostate cancer is based on glandular differentiation and architectural patterns, not on cytological features like nuclear pleomorphism.

### Architectural Distinction

| Feature | Gleason Grade 3 | Gleason Grade 4 |
|---------|-----------------|------------------|
| Glandular pattern | Well-formed, infiltrative glands | Poorly formed, fused glands; cribriform; solid sheets |
| Gland borders | Irregular but still recognizable | Loss of glandular differentiation |
| Lumen formation | Present but may be irregular | Absent or minimal |
| Cytology | Mild nuclear enlargement | Marked nuclear pleomorphism |
| Infiltration pattern | Infiltrative but distinct | Infiltrative with loss of identity |

**High-Yield:** Grade 3 glands are still **recognizable as glands** despite irregular infiltration. Grade 4 shows **loss of glandular differentiation** with cribriform, fused, or solid patterns — this is the critical discriminator.

**Clinical Pearl:** Gleason score is calculated by adding the primary pattern (most common) and secondary pattern (second most common). A Gleason 3+4=7 has a better prognosis than 4+3=7, despite the same total score, because the dominant pattern is grade 3.

**Mnemonic:** **GULF** — Grade 3 = Glands Understandable; Grade 4 = Glands Lost/Fused.

### Why Perineural Invasion Is Not the Discriminator
Perineural invasion can be present in both grades and is a separate adverse feature, not a defining architectural criterion for grade assignment.

Answer

A. Well-formed glands with minimal nuclear pleomorphism

Answer

C. Cribriform pattern with solid areas but still recognizable glandular structures

Answer

D. Presence of perineural invasion

Which histological feature best distinguishes Gleason grade 3 from Gleason grade 4 prostate adenocarcinoma?

Explanation

Gleason Grading System: Grade 3 vs Grade 4

Architectural Distinction

Why Perineural Invasion Is Not the Discriminator

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Feature	Gleason Grade 3	Gleason Grade 4
Glandular pattern	Well-formed, infiltrative glands	Poorly formed, fused glands; cribriform; solid sheets
Gland borders	Irregular but still recognizable	Loss of glandular differentiation
Lumen formation	Present but may be irregular	Absent or minimal
Cytology	Mild nuclear enlargement	Marked nuclear pleomorphism
Infiltration pattern	Infiltrative but distinct	Infiltrative with loss of identity