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Breast Cancer Treatment (PDQ®)

  • Updated: 09/25/2014

Table 4. Pathologic (pN)a,b

pNXRegional lymph nodes cannot be assessed (e.g., previously removed or not removed for pathologic study).
pN0No regional lymph node metastasis identified histologically.
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 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+)Malignant cells in regional lymph node(s) ≤0.2 mm (detected by H&E or IHC including ITC).
pN0(mol–)No regional lymph node metastases histologically, negative molecular findings (RT-PCR).
pN0(mol+)Positive molecular findings (RT-PCR), but no regional lymph node metastases detected by histology or IHC.
pN1Micrometastases.
OR
Metastases in 1–3 axillary lymph nodes.
AND/OR
Metastases in internal mammary nodes with metastases detected by sentinel lymph node biopsy but not clinically detected.c
pN1miMicrometastases (>0.2 mm and/or >200 cells but none >2.0 mm).
pN1aMetastases in 1–3 axillary lymph nodes, at least one metastasis >2.0 mm.
pN1bMetastases in internal mammary nodes with micrometastases or macrometastases detected by sentinel lymph node biopsy but not clinically detected.c
pN1cMetastases in 1–3 axillary lymph nodes and in internal mammary lymph nodes with micrometastases or macrometastases detected by sentinel lymph node biopsy but not clinically detected.
pN2Metastases in 4–9 axillary lymph nodes.
OR
Metastases in clinically detectedd internal mammary lymph nodes in the absence of axillary lymph node metastases.
pN2aMetastases in 4–9 axillary lymph nodes (at least 1 tumor deposit >2 mm).
pN2bMetastases in clinically detectedd internal mammary lymph nodes in the absence of axillary lymph node metastases.
pN3Metastases in ≥10 axillary lymph nodes.
OR
Metastases in infraclavicular (level III axillary) lymph nodes.
OR
Metastases in clinically detectedc ipsilateral internal mammary lymph nodes in the presence of one or more positive level I, II axillary lymph nodes.
OR
Metastases in >3 axillary lymph nodes and in internal mammary lymph nodes with micrometastases or macrometastases detected by sentinel lymph node biopsy but not clinically detected.c
OR
Metastases in ipsilateral supraclavicular lymph nodes.
pN3aMetastases in ≥10 axillary lymph nodes (at least 1 tumor deposit >2.0 mm).
OR
Metastases to the infraclavicular (level III axillary lymph) nodes.
pN3bMetastases in clinically detectedd ipsilateral internal mammary lymph nodes in the presence of one or more positive axillary lymph nodes.
OR
Metastases in >3 axillary lymph nodes and in internal mammary lymph nodes with micrometastases or macrometastases detected by sentinel lymph node biopsy but not clinically detected.c
pN3cMetastases in ipsilateral supraclavicular lymph nodes.
Posttreatment ypN
–Posttreatment yp "N" should be evaluated as for clinical (pretreatment) "N" methods above. The modifier "SN" is used only if a sentinel node evaluation was performed after treatment. If no subscript is attached, it is assumed that the axillary nodal evaluation was by AND.
–The X classification will be used (ypNX) if no yp posttreatment SN or AND was performed.
–N categories are the same as those used for pN.

AND = axillary node dissection; H&E = hematoxylin and eosin stain; IHC = immunohistochemical; ITC = isolated tumor cells; RT-PCR = reverse transcriptase/polymerase chain reaction.
aReprinted with permission from AJCC: Breast. In: Edge SB, Byrd DR, Compton CC, et al., eds.: AJCC Cancer Staging Manual. 7th ed. New York, NY: Springer, 2010, pp 347-76.
bClassification is based on axillary lymph node dissection with or without sentinel lymph node biopsy. Classification based solely on sentinel lymph node biopsy without subsequent axillary lymph node dissection is designated (SN) for "sentinel node," for example, pN0(SN).
c"Not clinically detected" is defined as not detected by imaging studies (excluding lymphoscintigraphy) or not detected by clinical examination.
d"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 based on fine-needle aspiration biopsy with cytologic examination.