Radiation Oncology/Breast/Staging

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[edit] Staging

AJCC Staging, 6th edition (2002)
Tumor:

• T0 - no primary tumor found
• T1 =< 2 cm
  • T1mic ≤ 0.1 cm (microinvasive)
  • 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 (not including pectoralis muscle)
  • T4b Skin oedema (peau d'orange), ulceration, or satellite skin modules
  • T4c Both 4a and 4b
  • T4d Inflammatory carcinoma

Lymph nodes

Clinical staging		Pathologic staging
cN0	No lymph node metastases	pN0	No lymph node metastases
cN1	Movable ipsilateral axillary lymph nodes	pN1mi	Micrometastases (> 0.2mm but <= 2.0 mm)
		pN1a	1-3 axillary lymph nodes
		pN1b	Microscopic involvement of IM nodes (not clinically apparent) but no axillary nodes
		pN1c	1-3 axillary lymph nodes and microscopic involvement of IM nodes
cN2a	Ipsilateral axillary lymph nodes fixed or matted	pN2a	4-9 axillary lymph nodes
cN2b	Clinically apparent internal mammary nodes in the absence of axillary lymph node metastases	pN2b	Clinically apparent IM nodes in the absence of axillary lymph nodes
cN3a	Infraclavicular lymph nodes	pN3a	10 or more axillary lymph nodes; or infraclavicular lymph nodes
cN3b	Clinically apparent internal mammary nodes with axillary lymph node involvement	pN3b	Clinically apparent IM nodes in the presence of positive axillary nodes; or microscopic IM nodes and more than 3 axillary lymph nodes
cN3c	Supraclavicular lymph nodes	pN3c	Supraclavicular lymph nodes

Mnemonics: "A" Nodes are "A"xillary, "B" Nodes are internal "B"reast (eg IMNs), "C" Nodes are supra"C"lavicular - excludes N1 subgroups

Nodes:

• Isolated tumor cells (ITC) - small clusters of cells <= 0.2 mm, usually with no histologic evidence of malignant activity (such as proliferation or stromal reaction). Designated pN0. If IHC or PCR is performed, may be designated pN0(i+),pN0(i-),pN0(mol+),or pN0(mol-).
• Micrometastases (pN1mi) - > 0.2mm but <= 2.0 mm. May also be designated pN1mi(i+) or pN1mi(i-) if IHC is performed.

Distant metastasis:

• M0 No
• M1 Yes

Stage grouping:

• Stage 0: Tis
• Stage I: T1,N0,M0
• Stage IIA: T0-1,N1,M0 or T2,N0,M0
• Stage IIB: T2,N1,M0 or T3,N0,M0
• Stage IIIA: T3,N1,M0 or T0-3,N2,M0
• Stage IIIB: T4,any N,M0
• Stage IIIC: any T,N3,M0
• Stage IV: any T,any N,M1

Changes from previous staging editions:

• 5th edition AJCC
  • pN1a - micrometastases (<0.2 cm)
  • pN1bi - 1-3 nodes, < 2 cm
  • pN1bii - 4+ nodes, < 2 cm
  • pN1biii - extracapsular extension, < 2 cm
  • pN1biv - > 2 cm

[edit] New Classifications

For additional information, see Tissue microarrays (Breast/Breast overview)

Gene expression profiling is the basis for additional classification schemes.

• Luminal A type - ER+ and/or PR+, HER2–. Usually low grade. These express genes similar to normal cells lining breast ducts and glands
• Luminal B type - ER+ and/or PR+, HER2+. These are similar to luminal A, but grow faster and have a slightly poorer prognosis.
• Basal type - ER–, PR–, HER2–, cytokeratin 5/6 positive, and/or HER1+. Also known as "triple negative". Higher prevalence in young African American women.
• HER2 type - ER-, PR-, HER2+. Usually high histological grade.