Breast cancer staging:

➡️American Joint Committee on Cancer (AJCC) TNM Staging System 8^th edition 2017: ⁽⁶⁰⁾

 Primary Tumor (T) The T category of the primary tumor is defined by the same criteria regardless of whether it is based on clinical or pathological criteria, or both. The T category is based primarily on the size of the invasive component of the cancer. The maximum size of a tumor focus is used as an estimate of disease volume. The largest contiguous dimension of a tumor focus is used, and small satellite foci of noncontiguous tumor are not added to the size. The cellular fibrous reaction to invasive tumor cells is generally included in the measurement of a tumor prior to treatment; however, the dense fibrosis observed following neoadjuvant treatment is generally not included in the pathological measurement because its extent may overestimate the residual tumor volume. The clinical size of a primary tumor (T) can be measured based on clinical findings (physical examination and imaging modalities, such as mammography, ultrasound, and MR imaging) and pathological findings (gross and microscopic measurements). Clinical tumor size (cT) should be based on the clinical findings that are judged to be most accurate for a particular case, although it may still be somewhat inaccurate because the intent of some breast cancers is not always apparent with current imaging techniques and because tumors are composed of varying proportions of noninvasive and invasive disease, which these techniques are currently unable to distinguish. Size should be measured to the nearest millimeter. If the tumor size is slightly less than or greater than a cutoff for a given T classification the size should be rounded to the millimeter reading that is closest to the cutoff. For example, a reported size of 4.9 mm is reported as 5 mm, or a size of 2.04 cm is reported as 2.0 cm (20 mm). The exception to this rounding rule is for a breast tumor sized between 1.0 and 1.4 mm. These sizes are rounded up to 2 mm, because rounding down would result in the cancer’s being categorized as microinvasive carcinoma (T1mi) defined as a size of 1.0 mm or less.

➡️Definitions for T, N, M

TX Primary tumor cannot be assessed.

T0 No evidence of primary tumor

Tis (DCIS)* Ductal carcinoma in situ Tis (Paget) Paget disease of the nipple NOT associated with invasive carcinoma and/or carcinoma in situ (DCIS) 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 Tumor ≤20 mm in greatest dimension

T1mi Tumor ≤1 mm in greatest dimension

T1a Tumor >1 mm but ≤5 mm in greatest dimension (round any measurement >1.0–1.9 mm to 2 mm) T1b Tumor >5 mm but ≤10 mm in greatest dimension

T1c Tumor >10 mm but ≤20 mm in greatest dimension

T2 Tumor >20 mm but ≤50 mm in greatest dimension

T3 Tumor >50 mm in greatest dimension

T4 Tumor of any size with direct extension to the chest wall and/ or to the skin (ulceration or macroscopic nodules); invasion of the dermis alone does not qualify as T4

T4a Extension to the chest wall; invasion or adherence to pectoralis muscle in the absence of invasion of chest wall structures does not qualify as T4

T4b Ulceration and/or ipsilateral macroscopic satellite nodules and/or edema (including peau d’orange) of the skin that does not meet the criteria for inflammatory carcinoma

T4c Both T4a and T4b are present

T4d Inflammatory carcinoma

*Note: Lobular carcinoma in situ (LCIS) is a benign entity and is removed from TNM staging in the AJCC Cancer Staging Manual, 8th Edition

➡️Regional Lymph Nodes (N) Clinical (cN)

 cNX* Regional lymph nodes cannot be assessed (e.g., previously removed)

cN0 No regional lymph node metastases (by imaging or clinical examination)

cN1 Metastases to movable ipsilateral level I, II axillary lymph node(s)

cN1mi** Micro metastases (approximately 200 cells, larger than 0.2 mm, but none larger than 2.0 mm)

cN2 Metastases in ipsilateral level I, II axillary lymph nodes that are clinically fixed or matted: or in ipsilateral internal mammary nodes in the absence of axillary lymph node metastases.

cN2a Metastases in ipsilateral level I, II axillary lymph nodes fixed to one another (matted) or to other structures.

cN2b Metastases only in ipsilateral internal mammary nodes in the absence of axillary lymph node metastases

cN3 Metastases in ipsilateral infraclavicular (level III axillary) lymph node(s) with or without level I, II axillary lymph node involvement; or in ipsilateral internal mammary lymph node(s) with level I, II axillary lymph node metastases; or metastases in ipsilateral supraclavicular lymph node(s) with or without axillary or internal mammary lymph node involvement

cN3a Metastases in ipsilateral infraclavicular lymph node(s)

cN3b Metastases in ipsilateral internal mammary lymph node(s) and axillary lymph node(s)

cN3c Metastases in ipsilateral supraclavicular lymph node(s)

Note: (sn) and (f) suffixes should be added to the N category to denote confirmation of metastasis by sentinel node biopsy or fine needle aspiration/core needle biopsy respectively.

*The cNX category is used sparingly in cases where regional lymph nodes have previously been surgically removed or where there is no documentation of physical examination of the axilla.

**cN1mi is rarely used but may be appropriate in cases where sentinel node biopsy is performed before tumor resection, most likely to occur in cases treated with neoadjuvant therapy.

➡️Pathologic (pN)

pNX regional lymph nodes cannot be assessed (e.g., not removed for pathological study or previously removed)

pN0 No regional lymph node metastasis identified or ITCs only

pN0(i+) ITCs only (malignant cells clusters no larger than 0.2 mm) in regional lymph node(s)

pN0(mol+) Positive molecular findings by reverse transcriptase polymerase chain reaction (RT-PCR); no ITCs detected.

pN1 Micrometastases; or metastases in 1–3 axillary lymph nodes; and/or in clinically negative internal mammary nodes with micrometastases or macrometastases by sentinel lymph node biopsy

pN1mi Micrometastases (approximately 200 cells, larger than 0.2 mm, but none larger than 2.0 mm)

pN1a Metastases in 1–3 axillary lymph nodes, at least one metastasis larger than 2.0 mm

pN1b Metastases in ipsilateral internal mammary sentinel nodes, excluding ITCs pN1c pN1a and pN1b combined.

pN2 Metastases in 4–9 axillary lymph nodes; or positive ipsilateral internal mammary lymph nodes by imaging in the absence of axillary lymph node metastases

pN2a Metastases in 4–9 axillary lymph nodes (at least one tumor deposit larger than 2.0 mm)

pN2b Metastases in clinically detected internal mammary lymph nodes with or without microscopic confirmation; with pathologically negative axillary nodes

pN3 Metastases in 10 or more axillary lymph nodes; or in infraclavicular (level III axillary) lymph nodes; or positive ipsilateral internal mammary lymph nodes by imaging in the presence of one or more positive level I, II axillary lymph nodes; or in more than three axillary lymph nodes and micro metastases or macro metastases by sentinel lymph node biopsy in clinically negative ipsilateral internal mammary lymph nodes; or in ipsilateral supraclavicular lymph nodes

pN3a Metastases in 10 or more axillary lymph nodes (at least one tumor deposit larger than 2.0 mm); or metastases to the infraclavicular (level III axillary lymph) nodes

pN3b pN1a or pN2a in the presence of cN2b (positive internal mammary nodes by imaging); or pN2a in the presence of pN1b

pN3c Metastases in ipsilateral supraclavicular lymph nodes

Note: (sn) and (f) suffixes should be added to the N category to denote confirmation of metastasis by sentinel node biopsy or FNA/core needle biopsy respectively, with NO further resection of nodes

➡️Distant Metastasis (M)

M0 No clinical or radiographic evidence of distant metastases*

cM0(i+) No clinical or radiographic evidence of distant metastases in the presence of tumor cells or deposits no larger than 0.2 mm detected microscopically or by molecular techniques in circulating blood, bone marrow, or other nonregional nodal tissue in a patient without symptoms or signs of metastases

cM1 Distant metastases detected by clinical and radiographic means

pM1 Any histologically proven metastases in distant organs; or if in non-regional nodes, metastases greater than 0.2 mm

 AJCC Anatomic Stage Groups