Is the Gleason score based on tissue biopsy?

Gleason Score and Tissue Biopsy

Yes, the Gleason score is definitively based on tissue biopsy of the prostate, requiring histopathological examination of prostate tissue samples to determine the architectural patterns of cancer cells. 1, 2

How Gleason Scoring Works

The Gleason grading system is the standard method for grading prostate cancer and requires examination of prostate tissue obtained through:

• Prostate needle biopsies (most common initial diagnostic approach)
• Transurethral resection specimens
• Radical prostatectomy specimens

The scoring process involves:

1. Identifying the two most predominant histological growth patterns in the tissue sample
2. Assigning each pattern a grade from 1 to 5 based on the degree of architectural differentiation
3. Summing these two grades to obtain the Gleason score (range: 2-10)

For example, if the most common pattern is grade 3 and the second most common is grade 4, the Gleason score would be 3+4=7 2

Technical Details of Gleason Scoring

When evaluating biopsy specimens, pathologists must follow specific rules 1:

• The Gleason grade applies to the dominant growth patterns
• When three grades are present, the highest grade and the dominant grade should be used
• The modified Gleason score should indicate the proportion of grade 4 and 5 disease present

The pathology report for prostate biopsies should specify 1:

• Length of biopsy core in millimeters
• Quality of the sample (mentioning any breaks)
• Length of tumor involvement (in mm or as percentage of biopsy length)
• Gleason score
• Presence of any capsular, pericapsular or extraprostatic extension

Clinical Significance of Gleason Score

The Gleason score is critical for risk stratification and treatment planning 2:

• Low-risk: Gleason score ≤6, PSA <10 ng/mL, clinical stage T1-T2a
• Intermediate-risk: Gleason score 7, PSA 10-20 ng/mL, clinical stage T2b
• High-risk: Gleason score 8-10, PSA >20 ng/mL, clinical stage T2c or higher

Important clinical considerations:

• A Gleason score of 4+3=7 carries a worse prognosis than 3+4=7 2
• Tumors with tertiary Gleason grade 4 or 5 behave more aggressively 2
• Gleason score should not be assessed in patients who have received radiotherapy or hormonal therapy 1, 2

Accuracy of Biopsy Gleason Scores

Standard sextant biopsy has limitations in accurately predicting final Gleason scores:

• Concordance between biopsy and radical prostatectomy Gleason scores is approximately 46-50% with standard biopsies 3, 4
• Extended needle biopsy (12 cores) increases accuracy to approximately 70% 4
• Biopsy under-grading occurs in 24-39% of cases, while over-grading occurs in 6-11% 4

Emerging Technologies

While tissue biopsy remains the gold standard for Gleason scoring, research is exploring less invasive methods:

• MRI-based radiomic biomarkers may eventually allow non-invasive Gleason score prediction 5
• Photoacoustic spectral analysis shows promise for evaluating Gleason scores without tissue removal 6

However, these technologies remain investigational and have not replaced the need for tissue biopsy for accurate Gleason scoring.