Breast Tumours
(ICD‐O‐3 C50)

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
• Anatomical subsites
• Definition of the regional lymph nodes
• TNM clinical classification
• pTNM pathological classification
• G histopathological grading
• Stage
• Prognostic grid

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

Anatomical Subsites

1. Nipple (C50.0)
2. Central portion (C50.1)
3. Upper inner quadrant (C50.2)
4. Lower inner quadrant (C50.3)
5. Upper outer quadrant (C50.4)
6. Lower outer quadrant (C50.5)
7. Axillary tail (C50.6)

Regional Lymph Nodes

The regional lymph nodes are:

1. 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
2. Infraclavicular (subclavicular) (ipsilateral)
3. Internal mammary (ipsilateral): lymph nodes in the intercostal spaces along the edge of the sternum in the endothoracic fascia
4. Supraclavicular (ipsilateral)

Note

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

Note

N – Regional Lymph Nodes

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.

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.

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.

Stage^a

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