If your family history and results from prior diagnostic tests suggest concern for prostate cancer, your physician may recommend a biopsy of the prostate to assess both the presence of cancer and its potential aggressiveness.
During the biopsy, the physician uses a thin, hollow needle—introduced either through the rectum or the perineum, the tissue between the anus and the scrotum—to obtain small cylindrical samples of prostate tissue known as cores. These samples are dispatched to a laboratory, where a trained pathologist evaluates them microscopically. Should cancer cells be identified, the pathologist then assigns a Gleason Score to indicate the aggressiveness of the disease.
The Gleason Score reflects the degree to which prostate cancer cells deviate from normal glandular tissue. The scoring system is predicated on the architectural arrangement observed in the biopsy samples. Higher scores, which range from 6 to 10, correspond to increasingly disorganized tissue and a greater likelihood of rapid metastatic spread.
This scoring system may aid in selecting treatment recommendations by integrating it with complementary laboratory findings to gauge the likelihood of metastatic spread; these data collectively inform management options. Clinicians typically interpret the Gleason Score alongside multiple additional criteria to estimate likely outcomes and to tailor therapy.
Prostate cancers exhibit heterogeneity in cellular differentiation, resulting in histologically distinct cellular grades. The Gleason Score arises from the summation of the highest and the second predominant grades. The first, or primary, grade reflects the predominant growth pattern, whereas the second, or secondary, grade denotes the second most prevalent arrangement.
For instance, should the most prevalent grade in the biopsy present as grade 3 and the next most prevalent as grade 4, the resulting Gleason Score would be computed as 7.
The pathologist may observe that the predominant pattern of the malignant cells in one of your biopsy specimens conforms to Gleason pattern 3, with a small subpopulation corresponding to Gleason pattern 4. This finding would be represented diagnostically as Gleason Score 3+4=7, signifying that the majority of the neoplasm is composed of pattern 3 cells and the next largest tract of cells is of pattern 4.
Gleason Score
• Gleason 6 or lower (3+3) Low/Very Low Risk – The neoplastic cells are largely indistinguishable from normal prostatic cells and are expected to exhibit indolent or non-existent progression.
• Gleason 7 (3+4) Intermediate Risk – The neoplasm is likely to exhibit an intermediate rate of progression. With a principle finding of 3 and a secondary of 4, the prognosis remains favorable; significant progression is often measured in years and definitive intervention is typically deferred until the latent phase.
• Gleason 8 (4+4, 3+5, 5+3) High Risk – The neoplasm is categorically aggressive, with a tendency for rapid growth and dissemination.
• Gleason 9-10
(4+5, 5+4, 5+5) Very High Risk – The neoplastic cells exhibit marked architectural and nuclear atypia. This phenotype is characteristic of aggressive disease, associated with rapid growth and increased metastatic propensity.
The recently implemented prostate cancer grading system builds upon the Gleason classification and redefines prognostic stratification through simplified categorical groupings. This five-tier framework is calibrated to more accurately characterize low-burden disease and thereby minimize overtreatment of indolent neoplasms.
• Gleason 3+3 = 6 – Grade 1
• Gleason 3+4 = 7 – Grade 2
• Gleason 4+3 = 7 – Grade 3
• Gleason 4+4, 3+5, 5+3 = 8 – Grade 4
• Gleason 4+5, 5+4, 5+5 = 9/10 – Grade 5
| The Traditional Gleason Score | New Grading System Group |
|---|---|
| Gleason 3+3=6 Only individual discrete well-formed glands | Grade 1 |
| Gleason 3+4=7 Predominantly well-formed glands with a lesser component of poorly-formed/fused/cribriform glands. | Grade 2 |
| Gleason 4+3=7 Predominantly poorly-formed/fused/cribriform glands with a lesser component of well-formed glands. | Grade 3 |
| Gleason 4+4=8 Only poorly-formed/fused/cribriform glands or: Predominantly well-formed glands with a lesser component lacking or, Predominantly lacking glands with a lesser component of well-formed glands. | Grade 4 |
| Gleason 9–10 Lacks gland formation (or with necrosis) with or without poorly-formed/fused/cribriform gland. | Grade 5 |
The Gleason Score is a useful measurement to predict the behavior of prostate cancer. Your doctor may use the grading to plan the best treatment in combination with other factors such as:
• Extent of tumor localization (stage)
• Serum prostate-specific antigen (PSA) concentration
• Patient's general health and chronological age
• Involvement of distant organ systems
• Unilateral versus bilateral prostate involvement
• Patient preferences regarding the initiation or deferral of therapy