Diagnostic classification of cancer
Once diagnosed, the tumor is classified.
In general, it assesses the extent of the tumor using the TNM system.
The TNM system is based on three elements
T: extent of primary tumor
N: the absence or presence and extent of metastasis to regional lymph nodes
M: absence or presence of distant metastases
The addition of numbers to these 3 components indicates the size of the tumor, namely T0, T1, T2, T3, T4 N0, N1, N2, N3 M0, M1 (in increasing severity).
Obviously, however, the staging is also used to deliver the most appropriate therapy to the patient.
The same T2N0M0 tumor might respond to therapy differently depending on some parameters such as genetic variants of receptors for hormones or the levels of specific protein markers of cell multiplication.