Pathologically adenocarcinomas account for more than 95% of prostate cancers. Almost 70% of the prostate cancer arise from the peripheral zone of the prostate gland and the remaining prostate cancers arise from the transition zone. Often those arising from the peripheral zone are more aggressive while those from the transition zone are less aggressive. The pathologic evaluation of biopsied prostate tissue is traditionally done using Gleason Scoring. The microscopic evaluation of prostate tissue with careful histologic grading is very important factor in assessing the outcomes in prostatic cancer.
Gleason Scores for Prostate Cancer
Evaluation of the architectural details of individual cancer glands is carried out in Gleason Scoring. Five distinct patterns of growth are described in the Gleason scoring. This includes pattern 1 which denotes tissue which is well differentiated with glandular appearance to pattern 5 which stands for the poorly differentiated variety with a loss of glandular structure. The final Gleason score is calculated by the sum of the grades of the most common and second most common growth patterns. The Gleason score values can range from 2 to 10. The tumors are classified based on the Gleason scores :
- well differentiated : scores 2 to 4
- intermediate differentiation : scores 5 to 7
- poorly differentiated : scores 8 to 10
Staging of Prostate Cancer
The staging of Prostate cancer is done using the AJCC TNM classification. Clinical staging of prostate cancer is based on findings of physical examination, the radiological studies and the pathology. Read more on prostate cancer diagnosis.
T, N and M Categories
- T1 in prostate cancer is when the tumor is not palpable on digital rectal examination (DRE) but detected only on pathologic examination. It is discovered incidentally after removal of prostate for benign prostatic hypertrophy (T1a and T1b) or on a biopsy specimen taken for evaluation following an elevated PSA level (T1c).
- T2 is when a palpable tumor can be detected during DRE but it is limited to the prostate (T2a shows tumor in one lobe and T2b in two lobes).
- T3 is a tumor extending through the prostate capsule. Focal involvement of the capsule is T3a and involvement of seminal vesicle is T3b.
- T4 are tumors invading adjacent structures like bladder neck, rectum and so on.
- N0 indicates that there is no spread to the lymph node(s).
- N1 indicates spread to pelvic lymph node(s).
- M0 denotes cancer that has not spread beyond the regional lymph nodes.
- M1 denotes cancer that has spread beyond the pelvic lymph nodes with M1a indicating distant lymph node involvement, M1b for cancer spread to the bones and M1C for spread to spread to distant sites.
Stages of Prostate Cancer
Stage I and stage II indicates a clinically localized cancer, devoid of any lymph node (N0) or distant spread (M0). The tumor is confined to prostate without extending to the prostate capsule. Stage III corresponds to a T3 tumor without any lymph node spread (No) or distant spread (M0). A stage IV tumor includes T4 tumors and tumors of any T stage with node spread (N1) or metastatic spread falls under stage IV (M1).