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Breast Tumours

TNM 7 classification

TNM 6 classification

1. 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
  • R Classification
  • Stage grouping
  • Summary

2. 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

3. 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)

4. 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:
    • I. Level I (low-axilla): lymph nodes lateral to the lateral border of pectoralis minor muscle.
    • II. Level II (mid-axilla): lymph nodes between the medial and lateral borders of the pectoralis minor muscle and the interpectoral (Rotter) lymph nodes.
    • III. 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.
    Note: Intramammary lymph nodes are coded as axillary lymph nodes.

  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).
Any other lymph node metastasis is coded as a distant metastasis (M1), including cervical or contralateral internal mammary lymph nodes.

5. TNM Clinical Classification

5.1. 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 situ
Tis (Paget). Paget disease of the nipple with no tumour
Note: Paget disease associated with a tumour is classified according to the size of the tumour.
T1. Tumour 2 cm or less in greatest dimension
T1mic. Microinvasion 0.1 cm or less in greatest dimension
Note: 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.
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. Tumour more than 5 cm in greatest dimension
T4. Tumour of any size with direct extension to chest wall or skin only as described in T4a to T4d
Note: Chest wall includes ribs, intercostal muscles, and serratus anterior muscle but not pectoral muscle.
T4a. Extension to chest wall
T4b. Oedema (including peau d'orange), or ulceration of the skin of the breast, or satellite skin nodules confined to the same breast
T4c. Both 4a and 4b, above
T4d. Inflammatory carcinoma
Note: 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.

5.2. 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 axillary lymph node(s)
N2. Metastasis in fixed ipsilateral axillary lymph node(s) or in clinically apparent* 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 or to other structures
N2b. Metastasis only in clinically apparent* internal mammary lymph node(s) and in the absence of clinically evident axillary lymph node metastasis
N3. Metastasis in ipsilateral infraclavicular lymph node(s) with or without axillary lymph node involvement; or in clinically apparent* ipsilateral internal mammary lymph node(s) in the presence of clinically evident 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 apparent is defined as detected by imaging studies (excluding lymphoscintigraphy) or by clinical examination or grossly visible pathologically.]

5.3. M - Distant Metastasis

MX. Distant metastasis cannot be assessed
M0. No distant metastasis
M1. Distant metastasis

6. pTNM Pathological Classification

See also: Additional site-specific recommendations for pT and pN

6.1. 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.

6.2. pN - Regional Lymph Nodes

The pathological classification requires the resection and examination of at least the low axillary lymph nodes (level I) (see Regional Lymph Nodes). 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.

Examination of one or more sentinel lymph nodes may be used for pathological classification. If classification is based solely on sentinel node biopsy without subsequent axillary lymph node dissection it should be designated (sn) for sentinel node, e.g., pN1(sn). (See of the Introduction.)

pNX. Regional lymph nodes cannot be assessed (not removed for study or previously removed)
pN0. No regional lymph node metastasis
pN1mi. Micrometastasis (larger than 0.2 mm, but none larger than 2 mm in greatest dimension)
pN1. Metastasis in 1-3 ipsilateral axillary lymph node(s), and/or in ipsilateral internal mammary nodes with microscopic metastasis detected by sentinel lymph node dissection but not clinically apparent**
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 with microscopic metastasis detected by sentinel lymph node dissection but not clinically apparent**
pN1c. Metastasis in 1-3 axillary lymph nodes and internal mammary lymph nodes with microscopic metastasis detected by sentinel lymph node dissection but not clinically apparent**
pN2. Metastasis in 4-9 ipsilateral axillary lymph nodes, or in clinically apparent* 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 apparent internal mammary lymph node(s), in the absence of axillary lymph node metastasis
pN3. Metastasis in 10 or more ipsilateral axillary lymph nodes; or in ipsilateral infraclavicular lymph nodes; or in clinically apparent ipsilateral internal mammary lymph nodes in the presence of one or more positive axillary lymph nodes; or in more than 3 axillary lymph nodes with clinically negative, microscopic metastasis in internal mammary lymph nodes; or in ipsilateral supraclavicular lymph nodes
pN3a. Metastasis in 10 or more axillary lymph nodes (at least one larger than 2 mm) or metastasis in infraclavicular lymph nodes
pN3b. Metastasis in clinically apparent internal 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 metastasis detected by sentinel lymph node dissection but not clinically apparent
pN3c. Metastasis in supraclavicular lymph node(s)

* [Note: Clinically apparent is defined as detected by imaging studies (excluding lymphoscintigraphy) or by clinical examination.]

** [Note: Not clinically apparent is defined as not detected by imaging studies (excluding lymphoscintigraphy) or by clinical examination.]

6.3. pM - Distant Metastasis

The pM categories correspond to the M categories.

7. G Histopathological Grading

For histopathological grading of invasive carcinoma see: Elston CW, Ellis IO. Pathological prognostic factors in breast cancer. I. The value of histological grade in breast cancer: experience from a large study with long-term follow-up. Histopathology 1991;19:403-410.

8. R Classification

The absence or presence of residual tumour after treatment is described by the symbol R. The definitions of the R classification are:

RX. Presence of residual tumour cannot be assessed
R0. No residual tumour
R1. Microscopic residual tumour
R2. Macroscopic residual tumour

9. Stage Grouping

Stage 0
Tis
N0
M0
Stage I
T1*
N0
M0
Stage IIA
T0
N1
M0
T1 *
N1
M0
T2
N0
M0
Stage IIB
T2
N1
M0
T3
N0
M0
Stage IIIA
T0
N2
M0
T1 *
N2
M0
T2
N2
M0
T3
N1, N2
M0
Stage IIIB
T4
N0, N1, N2
M0
Stage IIIC
Any T
N3
M0
Stage IV
Any T
Any N
M1
Note:* T1 includes T1mic.

10. Summary

Breast
Tis
In situ
T1
≤2 cm
T1mic
≤ 0.1 cm
T1a
>0.1 to 0.5 cm
T1b
>0.5 to 1 cm
T1c
>1 to 2 cm
T2
>2 to 5 cm
T3
>5 cm
T4
Chest wall/skin
T4a
Chest wall
T4b
Skin oedema/ulceration, satellite skin nodules
T4c
Both 4a and 4b
T4d
Inflammatory carcinoma
N1
Movable axillary
pN1mi
Micrometastasis, >0.2 mm ≤ 2 mm
pN1a
1-3 axillary nodes
pN1b
Internal mammary nodes with microscopic metastasis by sentinel node biopsy but not clinically apparent
pN1c
1-3 axillary nodes and internal mammary nodes with microscopic metastasis by sentinel node biopsy but not clinically apparent
N2a
Fixed axillary
pN2a
4-9 axillary nodes
N2b
Internal mammary clinically apparent
pN2b
Internal mammary nodes, clinically apparent, without axillary nodes
N3a
Infra-clavicular
pN3a
≥10 axillary nodes or infraclavicular node(s)
N3b
Internal mammary and axillary
pN3b
Internal mammary nodes, clinically apparent, with axillary node(s) or >3 axillary nodes and internal mammary nodes with microscopic metastasis by sentinal node biopsy but not clinically apparent
N3c
Supra-clavicular
pN3c
Supraclavicular