The TNM classification describes the size and extent of the tumor as well as the spread of cancer cells in other organs. The classification into different stages is based on three criteria:
T1: The tumor is neither palpable nor detectable by imaging techniques (ultrasound, MRI, CT).
T2: The tumor is palpable or visible on ultrasound, but still confined to the prostate gland
T3: The tumor has already broken through the prostate capsule and grown into the connective tissue around the prostate or seminal vesicle
T4: The tumor has spread even further into neighboring organs such as the urinary bladder or intestine
N0: The adjacent lymph nodes are tumor-free
N1: The adjacent lymph nodes are
M0: No metastases are present
M1: Metastases are present
For example, T1 N0 M0 would mean a small tumor with no lymph node involvement and no metastases.