Prostate Gleason Grading
Pattern-based Gleason score and Grade Group, with pattern-4 % bucketing, cribriform flag, and an HPF-based extent calculator.
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It is recommended that Gleason scores be assigned for each separately identified needle biopsy site, including each MRI-targeted lesion. This calculator is a pathology decision-support and educational tool for a single site/specimen. It does not replace the current CAP protocol, ISUP/GUPS recommendations, or professional pathologist judgment.
Reference
Gleason score construction
Gleason score = primary (most predominant) Gleason grade + worst (of the non-predominant) Gleason grade. Where no secondary grade exists, the primary grade is doubled. Report primary and secondary grades alongside the score, e.g. "Gleason score 7(3+4)" or "7(4+3)" — order matters.
Baseline two-pattern scoring (predominant pattern + the other pattern present, when that other pattern is ≥5% of tumor) is standard Gleason methodology assumed by the source document; the rules below are the source’s specific refinements to that baseline.
| Scenario | Rule |
|---|---|
| Minor secondary, <5% of tumor, higher grade | Report it — e.g. >95% pattern 3 + <5% pattern 4 → Gleason score 7(3+4). |
| Minor secondary, <5% of tumor, lower grade | Need not be reported — e.g. >95% pattern 4 + <5% pattern 3 → Gleason score 8(4+4), not diluted. |
| More than 2 patterns, worst grade is neither predominant nor the standard secondary | Choose predominant + highest grade present — e.g. 75% pattern 3, 20–25% pattern 4, <5% pattern 5 → scored 3+5=8, not 3+4=7. |
Grade Group table
Transcription note: the source table’s footnote for cases with >95% poorly formed/fused/cribriform glands (the <5% well-formed component not factored into the grade → Grade Group 4) appeared at the Grade Group 5 row in the supplied excerpt. This calculator applies it to the 4+4=8 scenario specifically — not as an instruction to reclassify Grade Group 5 cases.
| Grade Group | Gleason Score | Definition |
|---|---|---|
| 1 | ≤6 | Only individual discrete well-formed glands. |
| 2 | 3+4=7 | Predominantly well-formed glands with a lesser component of poorly formed/fused/cribriform glands. |
| 3 | 4+3=7 | Predominantly poorly formed/fused/cribriform glands with a lesser component of well-formed glands. |
| 4 | 4+4=8 / 3+5=8 / 5+3=8 | Only poorly formed/fused/cribriform glands (4+4); or predominantly well-formed glands with a lesser component lacking glands or with necrosis (3+5); or predominantly lacking glands/necrosis with a lesser component of well-formed glands (5+3). |
| 5 | 9–10 | Lack gland formation (or with necrosis), with or without poorly formed/fused/cribriform glands. |
Pattern identification features
The histologic features offered for each pattern are drawn from the architectural descriptors used in the source’s Grade Group table (well-formed glands; poorly-formed/fused/cribriform/glomeruloid glands; lacking gland formation or necrosis) and the four named Gleason pattern 4 architectures. They are an identification aid recorded in the report — not a complete, formally separate pattern definition — and do not block calculation. Patterns 1–2 are not used in contemporary practice.
Percentage by linear extent, including HPF-based conversion
Measuring the linear extent (mm) of each pattern along the core and calculating percentage as (pattern extent ÷ total tumor extent) × 100 is standard practical methodology — not itself a rule stated in the source excerpt, but an alternative to direct percentage estimation.
HPF-based extent: extent (mm) = HPFs spanned × the microscope’s field diameter — the same field-diameter-based conversion used in the suite’s mitotic-rate tools, applied to a linear span rather than an area.
Pattern 4 percentage reporting
Required for all Gleason score 7 (3+4, 4+3) cases. Recommended method: report as 5% or less, or 10% or less, then in 10% increments thereafter. This stratifies Gleason score 7 and identifies cases with limited pattern 4 (e.g. <10%, potentially eligible for active surveillance) versus extensive pattern 4 (e.g. >80%).
Limited focus: where cancer involves less than 10% of a core, grading and percent-pattern-4 reporting should be made with caution, with a comment that the focus is too small to accurately assign a percentage.
Cribriform architecture is an independent predictor of poorer outcome, particularly in Gleason score 7 tumors — report its presence explicitly.
Treatment effect
The Gleason system is recommended for all prostatic adenocarcinoma except where treatment effect is present (usually hormonal ablation or radiation). Grading may still be applied to new-onset (de novo) cancers lacking treatment effect, even in a post-treatment setting.
Case-level reporting: highest, composite & global grade
For case-level reporting across multiple positive cores. These are aggregate-grading concepts based on topographic correlation and morphologic judgment — not a formula, and not computed by this tool.
Targeted biopsies: the grade of the sampled lesion is already equivalent to the composite grade — global grade is not applicable. When systematic and targeted biopsies from the same case show different scores, either a global grade or a composite grade that factors in both may be reported.
| Grade | Definition |
|---|---|
| Highest | The single highest grade found among all positive cores/sites in the case. |
| Composite | Aggregate grade that accounts for the contiguous topographic location of positive sites (the presumed dominant nodule), similarity of morphology in adjacent cores and the extent of each. Avoids dilution by separate lower-grade cancers in non-contiguous cores; correlates better with radical prostatectomy grade than global grade. |
| Global | Aggregate grade that considers all positive sites, regardless of topography. |
Sources
Humphrey P, Amin MB, Berney D, Billis A, et al. Acinar adenocarcinoma. In: Moch H, Humphrey PA, Ulbright T, Reuter VE, eds. Pathology and Genetics: Tumours of the Urinary System and Male Genital Organs. 4th edition. WHO Classification of Tumours. Zurich, Switzerland: WHO Press; 2015:3-28.
Gleason DF, Mellinger GT, the Veterans Administration Cooperative Urological Research Group. Prediction of prognosis for prostatic adenocarcinoma by combined histological grading and clinical staging. J Urol. 1974;111:58-64.
College of American Pathologists (CAP). Protocol for the Examination of Specimens From Patients With Carcinoma of the Prostate Gland — Needle Biopsy/Case Level (document Prostate.Needle.Case.Bx_1.1.0.0.REL_CAPCP).
The source excerpt cites further references for the ISUP/GUPS consensus recommendations, active-surveillance nomograms (Kattan, Partin tables), cribriform pattern standardization and Grade Group validation studies; consult the complete published protocol for exact references.