Breast cancer staging

This article deals with breast cancer staging.

An introduction to cancer staging is in the cancer staging article. An introduction to breast pathology is in the breast pathology article.

T stage

Tumour:

• pT1: <= 20 mm.
  • pT1mic <= 1 mm.
  • pT1a > 1 mm and <= 5 mm.
  • pT1b > 5 mm and <= 10 mm.
  • pT1c > 10 mm and <= 20 mm.
• pT2: > 20 mm and <= 50 mm
• pT3: > 50 mm.
• pT4: chest wall or skin involvement.

Notes:

• Values should be rounded to the nearest millimetre.
  • Therefore:
    • 1.4 mm would be pT1mic.
    • 1.5 mm would be pT1a.

N stage

Sampling usually selective, i.e. sentinel lymph nodes only. ===Indications for lymph node sampling===

• Extensive DCIS.
• Biopsy suspicious for invasion or with microinvasion.
• Clinical findings (large palable mass) or radiology findings (irregular features) suggestive of invasion.
• Planned mastectomy.

Definitions

Definitions:

• Isolated tumour cells: <=0.2 mm or <=200 cells -- in a single cross-section. †
• Micrometastasis: <=0.2 cm and ( >0.2 mm or >200 cells ).
• Macrometastasis: >0.2 cm.

Notes:

• † The American Cancer Society web site says "or". The CAP protocol says "and/or" and notes it is all subjective.
• Isolated tumour cells are essentially ignored if the there is at least one macrometastasis.

Details

Lymph nodes:

• pN0: nil.
  • pN0(i+): <=0.2 mm and <200 cells.
• pN1: 1-3 axillary LNs or internal mammary LNs.
  • pN1mi: <=0.2 cm and ( >0.2 mm or >=200 cells ).
  • pN1a.
  • pN1b.
  • PN1c.
• pN2 4-9 positive LNs; internal mammary LNs or axillary LNs.
• pN3.

Sentinel lymph node sampling in breast cancer

Main articles: Sentinel lymph node and Lymph node metastasis

General

• Selective sampling of lymph nodes.
• Used for staging.
• Positive LNs = poorer prognosis.

Notes:

• If there is no palpable disease, there is no mortality benefit from axillary lymph node dissection, i.e. positive axillary lymph nodes can be left in situ without affecting outcome.
  • This does not negate the fact that a positive sentinel LN biopsy (vs. negative sentinel LN biopsy) portends a poorer prognosis.

Microscopic

Features:

• Atypical cells.
  • Nuclear changes of malignancy:
    • Nuclear enlargement + variation in size.
    • Variation in shape.
    • Hyperchromasia and variation in staining.
  • Usually in the subcapsular sinuses.

Pitfalls:

• Naevus cell rests.

IHC

Some hospitals use:

• CAM5.2 (LMWK) - to look for isolated tumour cells and small lymph node metstases.

Note:

• This is falling out of favour. The prognostic significance of isolated tumour cells is measurable but relatively small.^{[citation needed]}

M stage

Distant metastasis:

• cM0(i+) <=0.2 mm focus of tumour cells, without clinical signs and symptoms.
• pM1 focus of tumour cells > 0.2 mm.

See also

• Invasive breast cancer.
• Breast cancer grading.
• Cancer staging systems.