Grading is widely by the Gleason system. This involves five different patterns of differentiation, each given a number between 1-5. The two predominant patterns found within the tumour are identified, and their scores combined. The grade correlates well with the ultimate prognosis.
- Gleason grading system is based on glandular architecture - nuclear atypia is not evaluated
- Gleason grading system defines five histological patterns or grades with decreasing differentiation. The primary and secondary pattern, i.e. the most prevalent and the second most prevalent pattern, are added to obtain a Gleason score or sum
- Gleason pattern 1
- composed of a very well circumscribed nodule of separate, closely packed glands which do not infiltrate into adjacent benign prostatic tissue
- glands are of intermediate size, and similar in size and shape
- pattern is usually seen in transition zone cancers
- Gleason pattern 1 is exceedingly rare
- Gleason pattern 2
- composed of round or oval glands with smooth ends. The glands are more loosely arranged and not quite as uniform in size and shape as those of Gleason pattern 1
- may be minimal invasion by neoplastic glands into the surrounding non-neoplastic prostatic tissue
- glands are of intermediate size and larger than in Gleason pattern 1
- variation in glandular size and separation between glands is less than that seen in pattern 3.
- Gleason pattern 2 is usually seen in transition zone cancers but may occasionally be found in the peripheral zone
- Gleason pattern 3
- the most common histological pattern
- the glands are more infiltrative and the distance between them is more variable than in patterns 1 and 2
- malignant glands often infiltrate between adjacent non-neoplastic glands
- glands of pattern 3 vary in size and shape and are often angular
- small glands are typical for pattern 3, but there may also be large, irregular glands
- each gland has an open lumen and is circumscribed by stroma
- Gleason pattern 4
- glands appear fused, cribriform or they may be poorly defined. Fused glands are composed of a group of glands that are no longer completely separated by stroma
- edge of a group of fused glands is scalloped and there are occasional thin strands of connective tissue within this group
- hypernephroid pattern described by Gleason is a rare variant of fused glands, with clear or very pale-staining cytoplasm
- Gleason pattern 5
- an almost complete loss of glandular lumina, with only occasional lumina apparent
- epithelium forms solid sheets, solid strands or single cells invading the stroma
- needle biopsy Gleason score also correlates with virtually all other pathological variables, including tumour volume and serum PSA levels and many molecular markers
- Gleason score is based on the sum of two numbers:
- the first number is the score of the most common tumour pattern, the second number is the score of the second most common pattern
- if there are three patterns the first number is the most common and the second is the one with the highest grade
- for example, if the most common tumor pattern was grade 3, but some cells were found to be grade 4, the Gleason Score would be 3+4 = 7
- Gleason Score ranges from 0 to 10, with 10 having the worst prognosis. For Gleason Score 7, a Gleason 4+3 is a more aggressive cancer than a Gleason 3+4. Also, there is not really any difference between the aggressiveness of a Gleason Score 9 or 10 tumor
- the low grade tumours are with a score of 5 or below ; intermediate grade with a score of 6 & high grade of 7 or more till 10. This is a prognostic scoring system
- Gleason scores of 7-10 are associated with worse prognoses, and tumours with Gleason scores 5-6 are associated with lower progression rates after definitive therapy
More details about the Gleason scoring system is provided in the linked item.
Staging by a TNM system.
T - Primary tumour:
- TX - primary tumour cannot be assessed
- T0 - no evidence of primary tumour
- T1 - clinically inapparent tumour not palpable or visible by imaging
- T2 - tumour confined within the prostate
- T3 - tumour extends through the prostate capsule
- T4 - tumour is fixed or invades adjacent structures other than seminal vesicles: external sphincter; rectum; levator muscles and/or pelvic wall
N - Regional nodal involvement:
- NX - Regional lymph nodes cannot be assessed
- N0 - No regional lymph node metastasis
- N1 - Regional lymph node metastasis
M - Metastases:
- MX - Distant metastasis cannot be assessed
- M0 - No distant metastasis
- M1 - Distant metastasis (1)
Preoperative staging is attempted with transrectal ultrasonography, CT and NMR scanning. An advance is that of transrectal ultrasonographically-guided biopsy of the seminal vesicles and prostatic capsule. This was reported to give a 94% positive predictive estimation of extracapsular disease.
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