Appendix 2: TNM Classification

Appendix 2: TNM Classification of Breast Tumours, 8th edition (2016)

TNM Clinical Classification

T Primary Tumour
TX Primary tumour cannot be assessed
T0 No evidence of primary tumour
Tis Carcinoma in situ
Tis (DCIS) Ductal carcinoma in situ
Tis (LCIS) Lobular carcinoma in situa
Tis    (Paget) Paget disease of the nipple not associated with invasive carcinoma and/or carcinoma in situ (DCIS and/or LCIS) in the underlying breast parenchyma. Carcinomas in the breast parenchyma associated with Paget disease are categorized based on the size and characteristics of the parenchymal disease, although the presence of Paget disease should still be noted. 
T1

Tumour 2 cm or less in greatest dimension

  • T1mi Microinvasion 0.1 cm or less in greatest dimensionb
  • T1a More than 0.1 cm but not more than 0.5 cm in greatest dimension
  • T1b More than 0.5 cm but not more than 1 cm in greatest dimension
  • T1c More than 1 cm but not more than 2 cm in greatest dimension
T2 Tumour more than 2 cm but not more than 5 cm in greatest dimension
T3 T3 Tumour more than 5 cm in greatest dimension
T4

Tumour of any size with direct extension to chest wall and/or to skin (ulceration or skin nodules)c

  • T4a Extension to chest wall (does not include pectoralis muscle invasion only)
  • T4b Ulceration, ipsilateral satellite skin nodules, or skin oedema (including peau d’orange)
  • T4c Both 4a and 4
  • T4d Inflammatory carcinomad

 

Note

a The AJCC exclude Tis (LCIS).
b Microinvasion is the extension of cancer cells beyond the basement membrane into the adjacent tissues with no focus more than 0.1 cm in greatest dimension. When there are multiple foci of microinvasion, the size of only the largest focus is used to classify the microinvasion. (Do not use the sum of all individual foci.) The presence of multiple foci of microinvasion should be noted, as it is with multiple larger invasive carcinomas.
c Invasion of the dermis alone does not qualify as T4. Chest wall includes ribs, intercostal muscles, and serratus anterior muscle but not pectoral muscle.
d Inflammatory carcinoma of the breast is characterized by diffuse, brawny induration of the skin with an erysipeloid edge, usually with no underlying mass. If the skin biopsy is negative and there is no localized measurable primary cancer, the T category is pTX when pathologically staging a clinical inflammatory carcinoma (T4d). Dimpling of the skin, nipple retraction, or other skin changes, except those in T4b and T4d, may occur in T1, T2, or T3 without affecting the classification.

N Regional Lymph Nodes
NX Regional lymph nodes cannot be assessed (e.g. previously removed) 
N0 No regional lymph node metastasis 
N1 Metastasis in movable ipsilateral level I, II axillary lymph node(s) 
N2

Metastasis in ipsilateral level I, II axillary lymph node(s) that are clinically fixed or matted; or in clinically detected* ipsilateral internal mammary lymph node(s) in the absence of clinically evident axillary lymph node metastasis 

  • N2a  Metastasis in axillary lymph node(s) fixed to one another (matted) or to other structures
  • N2b  Metastasis only in clinically detected* internal mammary lymph node(s) and in the absence of clinically detected axillary lymph node metastasis 

 

N3

Metastasis in ipsilateral infraclavicular (level III axillary) lymph node(s) with or without level I, II axillary lymph node involvement; or in clinically detected* ipsilateral internal mammary lymph node(s) with clinically evident level I, II axillary lymph node metastasis; or metastasis in ipsilateral supraclavicular lymph node(s) with or without axillary or internal mammary lymph node involvement 

  • N3a Metastasis in infraclavicular lymph node(s)
  • N3b Metastasis in internal mammary and axillary lymph nodes
  • N3c Metastasis in supraclavicular lymph node(s) 

Note

* Clinically detected is defined as detected by clinical examination or by imaging studies (excluding lymphoscintigraphy) and having characteristics highly suspicious for malignancy or a presumed pathological macrometastasis based on fine needle aspiration biopsy with cytological examination. Confirmation of clinically detected metastatic disease by fine needle aspiration without excision biopsy is designated with a (f) suffix, e.g. cN3a(f).

Excisional biopsy of a lymph node or biopsy of a sentinel node, in the absence of assignment of a PT, is classified as a clinical N, e.g. cN1. Pathological classification (pN) is used for excision or sentinel lymph node biopsy only in conjunction with a pathological T assignment.

M Distant Metastasis
M0 No distant metastasis
M1 Distant metastasis

pTNM Pathological Classification

 

 

pT Primary Tumour

The pathological classification requires the examination of the primary carcinoma with no gross tumour at the margins of resection. A case can be classified pT if there is only microscopic tumour in a margin.

The pT categories correspond to the T categories. 

Note
When classifying pT the tumour size is a measurement of the invasive component. If there is a large in situ component (e.g. 4 cm) and a small invasive component (e.g. 0.5 cm), the tumour is coded pT1a. 

pN

Regional Lymph Nodes

The pathological classification requires the resection and examination of at least the low axillary lymph nodes (level I). Such a resection will ordinarily include 6 or more lymph nodes. If the lymph nodes are negative, but the number ordinarily examined is not met, classify as pN0.

pNx Regional lymph nodes cannot be assessed (e.g. previously removed, or not removed for pathological study)
pN0 No regional lymph node metastasis*

Note

* Isolated tumour cell clusters (ITCs) are single tumour cells or small clusters of cells not more than 0.2mm in greatest extent that can be detected by routine H and E stains or Immunohistochemistry. An additional criterion has been proposed to include a cluster of fewer than 200 cells in a single histological cross section. Nodes containing only ITCs are excluded from the total positive node count for purposes of N classification and should be included in the total number of nodes evaluated.

pN1

Micrometastases; or metastases in 1 to 3 axillary ipsilateral lymph nodes; and/ or in internal mammary nodes with metastases detected by sentinel lymph node biopsy but not clinically detected*

  • pN1mi Micrometastases (larger than0.2mm and/or more than 200 cells, but none larger than 2.0 mm)
  • pN1a  Metastasis in 1–3 axillary lymph node(s), including at least one larger than 2 mm in greatest dimension
  • pN1b  Internal mammary lymph nodes
  • pN1c  Metastasis in 1–3 axillary lymph nodes and internal mammary lymph nodes 
pN2

Metastasis in 4–9 ipsilateral axillary lymph nodes, or in clinically detected* ipsilateral internal mammary lymph node(s) in the absence of axillary lymph node metastasis

  • pN2a  Metastasis in 4–9 axillary lymph nodes, including at least one that is larger than 2 mm
  • pN2b  Metastasis in clinically detected internal mammary lymph node(s), in the absence of axillary lymph node metastasis 
pN3
  • pN3a Metastasis in 10 or more ipsilateral axillary lymph nodes (at least one larger than 2 mm) or metastasis in infraclavicular lymph nodes 
  • pN3b  Metastasis in clinically detected* internal ipsilateral mammary lymph node(s) in the presence of positive axillary lymph node(s); or metastasis in more than 3 axillary lymph nodes and in internal mammary lymph nodes with microscopic or macroscopic metastasis detected by sentinel lymph node biopsy but not clinically detected 
  • pN3c Metastasis in ipsilateral supraclavicular lymph node(s)

 

Post-treatment yPN
  • Post-treatment yp ‘N’ should be evaluated as for clinical (pretreatment) ‘N’ methods (see Section N – Regional Lymph Nodes). The modifier ‘sn’ is used only if a sentinel node evaluation was performed after treatment. If no subscript is attached, it is assumed the axillary nodal evaluation was by axillary node dissection.
  • The X classification will be used (ypNX) if no yp post-treatment SN or axillary dissection was performed.
  • N categories are the same as those used for pN.

Note
*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 pathological macrometastasis based on fine needle aspiration biopsy with cytological examination. Not clinically detected is defined as not detected by imaging studies (excluding lymphoscintigraphy) or not detected by clinical examination.

G Histopathological Grading
For histopathological grading of invasive carcinoma the Nottingham Histological Score is recommended. 
Stagea
Stage 0 Tis N0 M0
Stage IA T1b N0 M0
Stage IB T0, T1 N1mi M0
Stage IIA

T0, T1

T2

N1

N0

M0

M0

Stage IIB

T2

T3

N1

N0

M0

M0

Stage IIIA T0, T1, T2 N2 M0

Note 

a The AJCC also publish a prognostic group for breast tumours. b T1 includes T1mi. 

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Last update: 13 October 2017