TxPrimary tumor cannot be assessed
T0No evidence of primary tumor
TisCarcinoma in situ
Tis (DCIS)Ductal carcinoma in situ
Tis (LCIS)Lobular carcinoma in situ
Tis Paget's diseasePaget's disease of the nipple with no tumor
T1Tumors < cm in greatest dimension
T1micMicroinvasion < 0.1 cm in greatest dimension
T1aTumor > 0.5 cm but not more than 1 cm in greatest dimension
T1cTumor > 1 cm and not more than 2 cm in greatest dimension
T2Tumor > 2 cm and not more than 5 cm in greatest dimension
T3Tumor > 5 cm in greatest dimension
T4Tumor of any size with direct extension to (a) chest wall or (b) only as described below
T4aExtension to chest wall, not including pectoralis muscle
T4bEdema (including peau d'orange) or ulceration of the skin of the breast or satellite skin nodules confined to the same breast
T4cBoth TT4a and TT4ba
T4dInflammatory carcinoma
REGIONAL LYMPH NODES (N)
NxRegional lymph nodes cannot be assessed (e.g., previously removed)
N0No regional lymph node metastasis
N1Metastasis to movable axillary lymph node(s)
N2Metastasis in ipsilateral axillary lymph nodes fixed or matted, or clinically apparent ipsilateral internal mammary nodes in the absence of clinically evident axillary lymph node metastasis
N2aMetastasis to ipsilateral axillary lymph nodes fixed to one another (matted) or to other structures
N2bMetastasis only in clinically apparent ipsilateral internal mammary nodes and in the absence of clinically evident axillary lymph node metastasis
N3Metastasis in ipsilateral infraclavicular lymph node(s) or clinically apparent ipsilateral internal mammary node(s) and in the presence of clinically evident axillary lymph node metastasis; or metastasis in ipsilateral supraclavicular lymph node(s) with or without axillary or internal mammary lymph node involvement
N3aMetastasis in ipsilateral infraclavicular lymph node(s) and axillary lymph node(s)
N3bMetastasis in ipsilateral internal mammary node(s) and axillary lymph nodes(s)
N3cMetastasis in ipsilateral supraclavicular lymph node(s)
PATHOLOGICAL CLASSIFICATION (PN)
pNxRegional lymph nodes cannot be assessed (e.g., previously removed or not removed for pathologic studies)
pN0No regional lymph node metastasis histologically, no additional examination for isolated tumor cells (ITC)
Note: ITC are defined as single tumor cells or small cell clusters not greater than 0.2mm, usually detected with immunohistochemistry (IHC) or molecular methods but that may be verified with H&E stains. ITCs do not usually show evidence of metastatic activity (e.g., proliferation or stromal reaction).
pN0(i-)No regional lymph node metastasis histologically, negative IHC
pN0(i+)No regional lymph node metastasis histologically, positive IHC, no IHC cluster > 0.2 mm
pN0(mol-)No regional lymph node metastasis histologically, negative molecular findings (RT-PCR)
pN0(mol+)No regional lymph node metastasis histologically, positive molecular findings (RT-PCR)
pN1milMicrometastasis (>0.2 mm, none > 2 mm)
pN1Metastasis in 1-3 axillary lymph nodes and/or internal mammary nodes with microscopic disease detected by sentinel lymph node dissection but not clinically apparent
pN1aMetastasis in 1-3 axillary lymph nodes
pN1bMetastasis in internal mammary lymph nodes with microscopic disease detected with sentinel lymph node dissection but not clinically apparent
pN1cMetastasis in 1-3 axillary lymph nodes and in internal mammary lymph nodes with microscopic disease detected with sentinel lymph node dissection but not clinically apparent (if associated with >3 positive axillary lymph nodes, the internal mammary nodes are classified as pN3b to reflect increased tumor burden)
pN2Metastasis
pN2aMetastasis in 4-9 axillary lymph nodes in clinically apparent internal mammary lymph nodes in the absence of axillary lymph node metastasis
pN2bMetastasis in clinically apparent internal mammary lymph nodes in the absence of axillary lymph node metastasis
pN3Metastasis to > 10 axillary lymph nodes, in infraclavicular lymph nodes, or in clinically apparent ipsilateral internal mammary lymph nodes in the presence of > 1 positive axillary lymph nodes; or in > 3 axillary lymph nodes with clinically negative microscopic metastasis in internal mammary lymph nodes; or in ipsilateral supraclavicular lymph nodes
pN3aMetastasis in > 10 axillary lymph odes (at least 1 tumor deposit > 2.0 mm) or metastasis to the infraclavicular lymph nodes
pN3bMetastasis in clinically apparent ipsilateral internal mammary lymph nodes in the presence of > 1 positive axillary lymph nodes; or in > 3 axillary lymph nodes and in internal mammary lymph nodes with microscopic disease detected with sentinel lymph node dissection but not clinically apparent
pN3cMetastasis in ipsilateral supraclavicular lymph nodes
DISTANT METASTASIS (M)
MxDistant metastasis cannot be assessed
M0No distant metastasis
M1Distant metastasis

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