Table I.

Criteria of T, N and M staging.

Staging	Tumor conditions
T staging
Tis in situ carcinoma	No palpable lump in the breast
T1	Maximum diameter of tumor: <2 cm
T2	Maximum diameter of tumor: 2–5 cm
T3	Maximum diameter of tumor: >5 cm
T4	Regardless of tumor size, it has already invaded the chest wall or skin
N staging
N0	No palpable regional lymph node
N1	Ipsilateral axillary lymph nodes swollen with activity
N2	Ipsilateral axillary lymph nodes swollen, fused to each other and even adhered to other tissues
N3	Ipsilateral internal mammary lymph nodes with metastasis
M staging
M0	No distant metastasis
M1	Distant metastasis including lymph node metastasis on ipsilateral clavicle