Introductory Notes The site is described under the following headings:
Rules for classification with the procedures for assessing T, N, and M categories; additional methods may be used when they enhance the accuracy of appraisal before treatment
Definition of the regional lymph nodes
TNM clinical classification
pTNM pathological classification
G histopathological grading
Rules for Classification
The classification applies only to carcinomas and concerns the male as well as the female breast. There should be histological confirmation of the disease. The anatomical subsite of origin should be recorded but is not considered in classification.
In the case of multiple simultaneous primary tumours in one breast, the tumour with the highest T category should be used for classification. Simultaneous bilateral breast cancers should be classified independently to permit division of cases by histological type.
The following are the procedures for assessing T, N, and M categories:
T categories Physical examination and imaging, e.g., mammography
N categories Physical examination and imaging
M categories Physical examination and imaging
Central portion (C50.1)
Upper inner quadrant (C50.2)
Lower inner quadrant (C50.3)
Upper outer quadrant (C50.4)
Lower outer quadrant (C50.5)
Axillary tail (C50.6)
Regional Lymph Nodes
The regional lymph nodes are:
Axillary (ipsilateral): interpectoral (Rotter) nodes and lymph nodes along the axillary vein and its tributaries, which may be divided into the following levels:
Level I (low axilla): lymph nodes lateral to the lateral border of pectoralis minor muscle
Level II (mid axilla): lymph nodes between the medial and lateral borders of the pectoralis minor muscle and the interpectoral (Rotter) lymph nodes
Level III (apical axilla): apical lymph nodes and those medial to the medial margin of the pectoralis minor muscle, excluding those designated as subclavicular or infraclavicular
Infraclavicular (subclavicular) (ipsilateral)
Internal mammary (ipsilateral): lymph nodes in the intercostal spaces along the edge of the sternum in the endothoracic fascia
Intramammary lymph nodes are coded as axillary lymph nodes level I. Any other lymph node metastasis is coded as a distant metastasis (M1), including cervical or contralateral internal mammary lymph nodes.
TNM Clinical Classification
T – Primary Tumour
Primary tumour cannot be assessed
No evidence of primary tumour
Carcinoma in situ
Ductal carcinoma in situ
Lobular carcinoma in situa
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.
Tumour 2 cm or less in greatest dimension
Microinvasion 0.1 cm or less in greatest dimensionb
More than 0.1 cm but not more than 0.5 cm in greatest dimension
More than 0.5 cm but not more than 1 cm in greatest dimension
More than 1 cm but not more than 2 cm in greatest dimension
Tumour more than 2 cm but not more than 5 cm in greatest dimension
Tumour more than 5 cm in greatest dimension
Tumour of any size with direct extension to chest wall and/or to skin (ulceration or skin nodules)c
Extension to chest wall (does not include pectoralis muscle invasion only)
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.
Invasion of the dermis alone does not qualify as T4. Chest wall includes ribs, intercostal muscles, and serratus anterior muscle but not pectoral muscle.
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
Regional lymph nodes cannot be assessed (e.g., previously removed)
No regional lymph node metastasis
Metastasis in movable ipsilateral level I, II axillary lymph node(s)
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
Metastasis in axillary lymph node(s) fixed to one another (matted) or to other structures
Metastasis only in clinically detected* internal mammary lymph node(s) and in the absence of clinically detected axillary lymph node metastasis
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
Metastasis in infraclavicular lymph node(s)
Metastasis in internal mammary and axillary lymph nodes
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 apathological 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) (see page 152). 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 (ITC) are single tumour cells or small clusters of cells not more than 0.2 mm 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.
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*
Micrometastases (larger than 0.2 mm and/or more than 200 cells, but none larger than 2.0 mm)
Metastasis in 1–3 axillary lymph node(s), including at least one larger than 2 mm in greatest dimension
Internal mammary lymph nodes
Metastasis in 1–3 axillary lymph nodes and internal mammary lymph nodes
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
Metastasis in 4–9 axillary lymph nodes, including at least one that is larger than 2 mm
Metastasis in clinically detected internal mammary lymph node(s), in the absence of axillary lymph node metastasis
Metastasis in 10 or more ipsilateral axillary lymph nodes (at least one larger than 2 mm) or metastasis in infraclavicular lymph nodes
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
Metastasis in ipsilateral supraclavicular lymph node(s)
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.
Notes * 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.
pM – Distant Metastasis pM0 Not a valid category
pM1 Distant metastasis microscopically confirmed
G Histopathological Grading For histopathological grading of invasive carcinoma the Nottingham Histological Score is recommended.
Notes a The AJCC also publish a prognostic group for breast tumours. b T1 includes T1mi.