Table 3. Elaboration of Tumor Spread Based on TNM Staging.

T	Tumor size
TX	The primary tumor cannot be assessed.
T0	No evidence of primary tumor.
Tis	Carcinoma in situ (DCIS, or Paget disease of the breast with no associated tumor mass)
T	Tumor is 2 cm (3/4 of an inch) or less across.
T1mi	Microinvasive carcinoma: tumor is 0.1 cm or less across.
T2	Tumor is more than 2 cm but not more than 5 cm (2 inches) across.
T3	Tumor is more than 5 cm across.
T4	Tumor of any size growing into the chest wall or skin.
N	Node involvement
NX	Nearby lymph nodes cannot be assessed.
N0	No spread to nearby lymph nodes.
N1	Cancer has spread to fewer than three lymph nodes located on the underarm or has spread to any number of lymph nodes located near the breastbone (internal mammary lymph nodes).
N2	Cancer has spread to four or more lymph nodes located on the underarm or has spread to lymph nodes located in the chest outside of the underarm.
N3	Cancer has spread to lymph nodes located in the neck.
M	Metastasis
MX	Distant spread cannot be assessed
M0	There is no evidence of distant metastases
M1	There is evidence of distant metastases.

TNM stage: tumor, node, metastasis stage; DCIS: ductal carcinoma in situ.