How are regional lymph nodes (N) in breast cancer staged?

Updated: Dec 27, 2019
  • Author: Pavani Chalasani, MD, MPH; Chief Editor: John V Kiluk, MD, FACS  more...
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Answer

Table. (Open Table in a new window)

Table. (Open Table in a new window)

Regional lymph nodes (N)

Clinical

cNX

Regional lymph nodes cannot be assessed (eg, previously removed)

cN0

No regional lymph node metastasis (on imaging or clinical examination)

cN1

Metastasis to movable ipsilateral level I, II axillary lymph node(s)

cN1mi

Micrometastases (approximately 200 cells, larger than 0.2 mm, but none larger than 2.0 mm)

cN2

Metastases in ipsilateral level I, II axillary lymph nodes that are clinically fixed or matted; or in ipsilateral internal mammary nodes in the absence of clinically evident axillary lymph node metastases

cN2a

Metastases in ipsilateral level I, II axillary lymph nodes fixed to one another (matted) or to other structures

cN2b

Metastases only in ipsilateral internal mammary nodes and in the absence of axillary lymph node metastases

cN3

Metastases in ipsilateral infraclavicular (level III axillary) lymph node(s), with or without level I, II axillary node involvement, or in ipsilateral internal mammary lymph node(s) with level I, II axillary lymph node metastasis; or metastases in ipsilateral supraclavicular lymph node(s), with or without axillary or internal mammary lymph node involvement

cN3a

Metastasis in ipsilateral infraclavicular lymph node(s)

cN3b

Metastasis in ipsilateral internal mammary lymph node(s) and axillary lymph node(s)

cN3c

Metastasis in ipsilateral supraclavicular lymph node(s)

Note: (sn) and (f) suffixes should be added to the N category to denote confirmation of metastasis by sentinel node biopsy or fine needle aspiration/core needle biopsy, respectively.

Pathologic (pN)

pNX

Regional lymph nodes cannot be assessed (for example, previously removed, or not removed for pathologic study)

pN0

No regional lymph node metastasis identified histologically, or isolated tumor cell clusters (ITCs) only. Note: ITCs are defined as small clusters of cells ≤ 0.2 mm, or single tumor cells, or a cluster of < 200 cells in a single histologic cross-section; ITCs may be detected by routine histology or by immunohistochemical (IHC) methods; nodes containing only ITCs are excluded from the total positive node count for purposes of N classification but should be included in the total number of nodes evaluated

pN0(i)

No regional lymph node metastases histologically, negative IHC

pN0(i+)

ITCs only in regional lymph node(s)

pN0(mol-)

No regional lymph node metastases histologically, negative molecular findings (reverse transcriptase polymerase chain reaction [RT-PCR])

pN0(mol+)

Positive molecular findings by RT-PCR; no ITCs detected 

pN1

Micrometastases; or metastases in 1-3 axillary lymph nodes and/or in internal mammary nodes; and/or in clinically negative internal mammary nodes with micrometastases or macrometastases by sentinel lymph node biopsy

pN1mi

Micrometastases (200 cells, > 0.2 mm but none > 2.0 mm)

pN1a

Metastases in 1-3 axillary lymph nodes (at least 1 metastasis > 2.0 mm)

pN1b

Metastases in ipsilateral internal mammary lymph nodes, excluding ITCs, detected by sentinel lymph node biopsy

pN1c

Metastases in 1-3 axillary lymph nodes and in internal mammary sentinel nodes (ie, pN1a and pN1b combined)

pN2

Metastases in 4-9 axillary lymph nodes; or positive ipsilateral internal mammary lymph nodes by imaging in the absence of axillary lymph node metastases

pN2a

Metastases in 4-9 axillary lymph nodes (at least 1 tumor deposit > 2.0 mm)

pN2b

Clinically detected* metastases in internal mammary lymph nodes with or without microscopic confirmation; with pathologically negative axillary lymph nodes

pN3

Metastases in ≥ 10 axillary lymph nodes; or in infraclavicular (level III axillary) lymph nodes; or positive ipsilateral internal mammary lymph nodes by imaging in the presence of one or more positive level I, II axillary lymph nodes; or in > 3 axillary lymph nodes and micrometastases or macrometastases by sentinel lymph node biopsy in clinically negative ipsilateral internal mammary lymph nodes; or in ipsilateral supraclavicular lymph nodes 

pN3a

Metastases in ≥ 10 axillary lymph nodes (at least 1 tumor deposit > 2.0 mm); or metastases to the infraclavicular (level III axillary lymph) nodes

pN3b

pN1a or pN2a in the presence of cN2b (positive internal mammary nodes by imaging) or pN2a in the presence of pN1b

pN3c

Metastases in ipsilateral supraclavicular lymph nodes

*"Clinically detected" is defined as detected by imaging studies (excluding lymphoscintigraphy) or by clinical examination and having characteristics highly suspicious for malignancy or a presumed pathologic macrometastasis on the basis of FNA biopsy with cytologic examination.