Gleason grade 4 prostate adenocarcinoma patterns: an interobserver agreement study among genitourinary pathologists

Area of Science:

• Pathology
• Urologic Oncology

Background:

• Accurate Gleason grading is crucial for prostate cancer prognosis and treatment decisions.
• Gleason grade 4 encompasses several distinct growth patterns, posing challenges for consistent interpretation.

Purpose of the Study:

• To evaluate the interobserver agreement among genitourinary pathologists on individual Gleason grade 4 growth patterns.
• To identify specific Gleason grade 4 patterns with low reproducibility.

Main Methods:

• Twenty-three genitourinary pathologists assessed 60 high-magnification images of prostate cancer tissue.
• Participants identified predominant Gleason grades and specific Gleason grade 4 growth patterns (ill-formed, fused, cribriform, glomeruloid).
• Agreement was defined as consensus (≥80%) or favored (60-80%) agreement.

Main Results:

• Overall consensus on Gleason grading was achieved in 78% of cases.
• Reproducibility varied significantly by Gleason grade 4 growth pattern: cribriform (23%) and glomeruloid (38%) showed higher agreement than fused (2%) and ill-formed (0%).
• A 'complex fused' pattern was identified as a borderline entity with no consensus.

Conclusions:

• Interobserver reproducibility for Gleason grade 4 growth patterns is inconsistent, particularly for ill-formed and fused patterns.
• Cribriform and glomeruloid patterns demonstrated better reproducibility, suggesting potential for more reliable classification.
• The 'complex fused' pattern requires further investigation due to its unclear prognostic significance and lack of consensus.