Table 2.
Evolution of the Gleason grading scale
| Pattern | Original Gleason five69 | 2005 ISUP modified Gleason system73 | Histological definition of 2014 ISUP modified Gleason system75 |
|---|---|---|---|
| 1 | Very well differentiated, small, closely packed, uniform glands in essentially circumscribed masses | Circumscribed, closely packed nodules with separate, uniform, rounded to oval, medium-sized acini (larger glands than pattern 3) | Only individual, discrete, well-formed glands (Gleason score ≤6) |
| 2 | Similar to pattern 1, but with moderate variations in size and shape of glands and more atypia in histological appearance in individual cells; cribriform pattern might be present, still essentially circumscribed, but more loosely arranged | Like pattern 1, fairly circumscribed, yet at the edge of the tumour nodule there might be minimal levels of infiltration; glands are more loosely arranged and not quite as uniform as in Gleason pattern 1 | Predominantly well-formed glands with a lesser component of poorly formed/fused/cribriform glands (Gleason score 3 + 4 = 7) |
| 3 | Similar to pattern 2, but with marked irregularity in size and shape of glands, with tiny glands or individual cells invading the stroma away from circumscribed masses, or solid cords and masses with easily identifiable differentiation within most glands | Discrete glandular units; typically smaller glands than seen in Gleason pattern 1 or 2; infiltrates in and amongst non-neoplastic prostate acini; marked variations in size and shape; smoothly circumscribed, small cribriform tumour nodules | Predominantly poorly formed/fused/cribriform glands with a lesser component of well-formed glandsa (Gleason score 4 + 3 = 7) |
| 4 | Large clear cells growing in a diffuse pattern resembling hypernephroma; might show signs of gland formation | Fused microacinar glands. Ill-defined glands with a poorly formed glandular lumina. Large cribriform glands, with an irregular border and a hypernephromatoid histological pattern | Only poorly formed/fused/cribriform glands or predominantly well-formed glands and a lesser component lacking in glandsb or predominantly lacking in glands and with a lesser component of well-formed glandsb (Gleason score 4 + 4 = 8; 3 + 5 = 8; or 5 + 3 = 8) |
| 5 | Very poorly differentiated tumours; usually solid masses or diffuse areas of growth with little or no differentiation into glands | Essentially no glandular differentiation, composed of solid sheets, cords, or single cells; comedocarcinoma of the prostate with central necrosis surrounded by papillary, cribriform, or solid masses | Lack of gland formation (or with necrosis) with or without poorly formed/fused/cribriform glands (Gleason scores 9–10) |
ISUP, International Society of Urological Pathology.
a
For cases with >95% poorly formed/fused/ cribriform glands or lack of glands on a core or at radical prostatectomy, the component of <5% well-formed glands is not factored into the grade.
b
Poorly-formed/fused/cribriform glands can be a more minor component.