Biopsy Slide Loaded — Scanning the Tissue
A stained biopsy core sits ready under the scope.
- 10–12: Core count (systematic needle biopsy)
- H&E: Stain used (hematoxylin and eosin)
- 4 µm: Section thickness (paraffin-embedded slice)
- 4–10x: Read magnification (low-to-medium power)
What the pathologist looks for
Glandular architecture, not single-cell detail, drives the grade.
Why architecture over cytology
Pattern arrangement proved more reproducible than nuclear grading.
Architecture-first grading has held up for nearly 60 years.
Primary Pattern Identified — The Dominant Architecture
Drag the primary slider — the majority pattern fills the field.
- >50%: Primary definition (most prevalent pattern)
- Round glands: Grade 3 look (discrete, single lumen)
- Fused glands: Grade 4 look (cribriform, glomeruloid)
- No glands: Grade 5 look (solid sheets, cords)
Spotting the majority pattern
Scan the whole core, estimate area covered by each pattern.
Grade 3 vs 4 vs 5 cues
Lumen loss and fusion mark the jump from 3 to 4 to 5.
Watch the tissue view redraw as you move the slider.
Secondary Pattern Identified — The Minority Architecture
The wedge region marks the second most common pattern.
- 2nd most: Secondary definition (next largest area)
- Grade 3: Reported floor (lowest grade used today)
- ~28%: Field split shown (wedge vs majority field)
- 3–5 scale: Both graded (same criteria as primary)
Same criteria, smaller area
Secondary pattern uses identical architectural cues, less tissue.
Single-pattern tumors
If only one pattern exists, it is simply doubled.
A pure grade-3 tumor is scored 3+3, not just 3.
Gleason Sum Calculated — Primary Plus Secondary
Primary grade and secondary grade are simply added together.
- P + S: Formula (primary plus secondary)
- 6–10: Reported range (contemporary biopsy practice)
- Both = 7: 3+4 vs 4+3 (but not the same disease)
- Yes: Order matters (first number is dominant)
Order encodes dominance
The first number is always the more prevalent pattern.
Why the sum can mislead
Same sum, different dominant pattern, different behavior.
4+3 behaves worse than 3+4 despite an identical sum.
Grade Group Assigned — The Modern Reporting Standard
The Gleason sum now maps onto one of five Grade Groups.
- Sum 6: Grade Group 1 (3+3, lowest risk)
- 3+4=7: Grade Group 2 (primary well-formed)
- 4+3=7: Grade Group 3 (primary fused/cribriform)
- 8 / 9–10: Grade Group 4/5 (highest-risk architecture)
Five groups, five outcomes
ISUP 2014 split sums into five clearly separated categories.
Why grouping replaced raw sums
Grade Group separates 3+4 from 4+3 cleanly.
Grade Group is now the standard label on pathology reports.