Topic Completed: 8 January 2019

Minor changes: 6 May 2021

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PubMed Search: Staging[title] breast carcinoma[title]

Emily S. Reisenbichler, M.D.
Debra L. Zynger, M.D.
Page views in 2020: 28,006
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Cite this page: Reisenbichler ES, Zynger D. Staging. website. Accessed October 28th, 2021.

Pathologic TNM staging of breast carcinoma, AJCC 8th edition
Definition / general
  • All carcinomas of the breast are covered by this staging system
  • Breast sarcomas, phyllodes tumor and breast lymphomas are not staged using this system
Essential features
  • AJCC 7th edition staging was sunset on December 31, 2017; as of January 1, 2018, use of the 8th edition is mandatory
ICD coding
  • ICD-10: C50.0 - nipple
  • ICD-10: C50.1 - central portion of breast
  • ICD-10: C50.2 - upper inner quadrant
  • ICD-10: C50.3 - lower inner quadrant
  • ICD-10: C50.4 - upper outer quadrant
  • ICD-10: C50.5 - lower outer quadrant
  • ICD-10: C50.6 - axillary tail
  • ICD-10: C50.8 - overlapping lesion of breast
  • ICD-10: C50.9 - breast, not otherwise specified
Primary tumor (pT)
  • pTX: cannot be assessed
  • pT0: no evidence of primary tumor
  • pTis: ductal carcinoma in situ, Padget disease, encapsulated papillary carcinoma and solid papillary carcinoma
    • pTis (DCIS): ductal carcinoma in situ without invasive carcinoma
    • pTis (Paget): Paget disease without invasive carcinoma
  • pT1mi: tumor ≤ 1 mm
  • pT1a: tumor > 1 mm but ≤ 5 mm
  • pT1b: tumor > 5 mm but ≤ 10 mm
  • pT1c: tumor > 10 mm but ≤ 20 mm
  • pT2: tumor > 20 mm but ≤ 50 mm
  • pT3: tumor > 50 mm
  • pT4a: extension to chest wall (not including pectoralis muscle)
  • pT4b: edema (including peau d'orange), ulceration of skin or ipsilateral satellite skin nodules
  • pT4c: both T4a and T4b
  • pT4d: inflammatory carcinoma (involves > 1/3 of the breast skin, primarily a clinical diagnosis)

  • Lobular carcinoma in situ (LCIS) is no longer classified as Tis and is now considered a risk factor, not a malignancy
  • For invasive tumors, do not include in situ tumor in the tumor measurement used to determine pT category
  • Round invasive tumor size to the nearest millimeter, except if between 1.0 and 1.4 mm, then round up to 2.0 mm to avoid classifying as pT1mi
  • Do not add tumor dimensions from the needle biopsy to the excision; use the maximum dimension in either the needle biopsy or excision for pT categorization (invasive tumor is larger in the needle biopsy than subsequent excision in 12% of cases, Am J Surg Pathol 2013;37:739)
  • If multiple excisions, may want to report "at least pT_, a more accurate estimate may be based on imaging studies"
  • If there are multiple simultaneous, macroscopically measurable, ipsilateral invasive tumors, use largest size, do not sum sizes; can use (m) suffix, e.g. pT1b(m)
  • Contiguous tumor within the pectoralis muscle should be included in the tumor measurement to determine pT category
  • In a postneoadjuvant specimen, measure the largest single contiguous focus; do not include the fibrous tumor bed without viable tumor
Regional lymph nodes (pN)
  • pNX: cannot be assessed
  • pN0: no regional lymph node metastasis histologically
  • pN0(i-): no regional lymph node metastasis by histology or immunohistochemistry
  • pN0(i+): isolated tumor cells (cluster ≤ 0.2 mm and < 200 cells)
  • pN0(mol+): RT-PCR positive but negative by light microscopy
  • pN1mi: micrometastasis (tumor deposit > 0.2 mm and ≤ 2.0 mm or ≤ 0.2 mm and > 200 cells)
  • pN1a: metastasis in 1 - 3 axillary lymph nodes with at least 1 tumor deposit > 2.0 mm
  • pN1b: metastasis in internal mammary sentinel lymph node with tumor deposit > 2.0 mm
  • pN1c: pN1a and pN1b
  • pN2a: metastasis in 4 - 9 axillary lymph nodes with at least 1 tumor deposit > 2.0 mm
  • pN2b: metastasis in clinically detected internal mammary nodes with pathologically negative axillary nodes
  • pN3a: metastasis in ≥ 10 axillary lymph nodes with at least 1 tumor deposit > 2.0 mm or metastasis to infraclavicular lymph node
  • pN3b: positive internal mammary node by imaging with pN1a or pN1b
  • pN3c: metastasis in ipsilateral supraclavicular lymph node

  • Regional lymph nodes include axillary, internal mammary, supraclavicular and intramammary
  • Isolated tumor cells = cluster ≤ 0.2 mm and < 200 cells
  • Micrometastasis = deposit > 0.2 mm and ≤ 2.0 mm or ≤ 0.2 mm and > 200 cells
  • Macrometastasis = deposit > 2.0 mm
  • Count cells or measure tumor within a single lymph node cross section
  • Measure only the largest contiguous focus of metastatic tumor cells; adjacent satellites are not included
  • Extranodal extension should be included in the tumor deposit measurement
  • Number of nodes with isolated tumor cells does not change pN category (e.g. 3 nodes with macrometastases plus 1 node with isolated tumor cells is pN1a, not pN2a)
  • Direct extension of tumor into an intramammary lymph node is included as a positive regional lymph node
  • Rounded tumor nodules without nodal tissue present in a nodal drainage area should be considered lymph nodes completely replaced with tumor, unless a vascular wall is present
  • "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 pathologic macrometastasis based on fine needle aspiration biopsy with cytologic examination
  • In a postneoadjuvant node, measure only the largest contiguous metastatic deposit; do not add separate tumor deposits or include fibrosis without viable tumor
Distant metastasis (M)
  • pM1: distant metastasis histologically proven > 0.2 mm
  • y: preoperative radiotherapy or chemotherapy
  • r: recurrent tumor stage
AJCC prognostic stage groups
  • pTNM, tumor grade, ER, PR and HER2 status are incorporated into prognostic stage groups to refine prognosis
  • Refer to the AJCC 8th edition for the stage group definitions
Registry data collection variables
Histologic grade (G)
  • GX: cannot be assessed
  • G1: low grade (score 3 - 5)
  • G2: intermediate grade (score 6 - 7)
  • G3: high grade (score 8 - 9)

  • To assign a histologic grade, assess and combine values for tubule formation (1 - 3), nuclear pleomorphism (1 - 3) and mitotic count (1 - 3) into a score
Microscopic (histologic) images

Contributed by Sucheta Srivastava, M.D.


Macrometastasis with extranodal extension


Isolated tumor cells, pancytokeratin

Additional references
Board review style question #1
What is the pN category for a patient with 1 macrometastasis, 2 micrometastases and 2 nodes with isolated tumor cells?

  1. pNX
  2. pN0(i+)
  3. pN1a
  4. pN2a
  5. pN3a
Board review style answer #1
C. pN1a. The number of nodes with isolated tumor cells does not increase the pN category.

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Reference: Breast - Staging
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