TNM (Tumour Node Metastasis) classification for CaP.
Tumour Node Metastasis (TNM) classification of CaP
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
T1a Tumour incidental histological finding in 5% or less of tissue resected
T1b Tumour incidental histological finding in more than 5% of tissue resected
T1c Tumour identified by needle biopsy (e.g., because of elevated prostate-specific antigen (PSA) level)
T2 Tumour confined within the prostate1
T2a Tumour involves one half of one lobe or less
T2b Tumour involves more than half of one lobe, but not both lobes
T2c Tumour involves both lobes
T3 Tumour extends through the prostatic capsule2
T3a Extracapsular extension (unilateral or bilateral)
T3b Tumour invades seminal vesicle(s)
T4 Tumour is fixed or invades adjacent structures other than seminal vesicles: bladder neck, external sphincter, rectum, levator muscles, or pelvic wall
N - Regional lymph nodes3
NX Regional lymph nodes cannot be assessed
N0 No regional lymph node metastasis
N1 Regional lymph node metastasis
M - Distant metastasis4
MX Distant metastasis cannot be assessed
M0 No distant metastasis
M1 Distant metastasis
M1a Non-regional lymph node(s)
M1b Bone(s)
M1c Other site(s)
1 Tumour found in one or both lobes by needle biopsy, but not palpable or visible by imaging, is classified as T1c.
2 Invasion into the prostatic apex, or into (but not beyond) the prostate capsule, is not classified as T3, but as T2.
3 Metastasis no larger than 0.2 cm can be designated pN1mi.
4 When more than one site of metastasis is present, the most advanced category should be used.

2.1 Gleason score
The most commonly used system for grading adenocarcinoma of the prostate is the Gleason score (2). Biopsy material (core biopsy or operative specimens) is required to be able to assess the Gleason score; cytological preparations cannot be used. The system describes a score between 2 and 10, with 2 being the least aggressive and 10 the most aggressive. This score is the sum of the two most common patterns (grades 1-5) of tumour growth found. In needle biopsy, it is now recommended that the worst grade always should be included even if present in < 5% (3).