Breast Cancer TNM Staging (AJCC 8th Edition)

The AJCC 8th Edition introduced a major paradigm shift in breast cancer staging: in addition to the traditional anatomic TNM grouping, a Prognostic Stage is now recommended that integrates tumor grade, estrogen receptor (ER), progesterone receptor (PR), HER2 status, and (for ER+/HER2− node-negative T1-T2 tumors) the Oncotype DX Recurrence Score. This dual-staging approach recognizes that molecular subtype substantially modifies prognosis beyond anatomy alone. The anatomic TNM stages range from Stage 0 (carcinoma in situ) through Stage IV (distant metastasis) across 8 anatomic groupings. Clinicians should report both the clinical/pathologic anatomic stage and the prognostic stage when biomarker data are available.

T Descriptors

• TX: Primary tumor cannot be assessed.
• T0: No evidence of primary tumor.
• Tis (DCIS): Ductal carcinoma in situ. DCIS is Stage 0. Treatment: breast-conserving surgery + radiotherapy, or mastectomy. Endocrine therapy for ER+ DCIS reduces ipsilateral recurrence.
• Tis (Paget): Paget disease of the nipple not associated with underlying invasive carcinoma or DCIS. If associated with DCIS or invasive carcinoma, stage accordingly.
• T1mi: Microinvasion ≤1 mm in greatest dimension. Prognosis essentially equivalent to DCIS; lymph node metastasis is exceedingly rare.
• T1a: Tumor >1 mm but ≤5 mm in greatest dimension (round up to nearest mm for decimals).
• T1b: Tumor >5 mm but ≤10 mm in greatest dimension.
• T1c: Tumor >10 mm but ≤20 mm in greatest dimension. T1c is the upper boundary of "early" breast cancer; T1cN0M0 = Stage IA anatomically.
• T2: Tumor >20 mm but ≤50 mm in greatest dimension. T2N0 = Stage IIA anatomically. Consider neoadjuvant chemotherapy for HER2+ or TNBC T2 tumors to maximize breast-conservation rates and pCR assessment.
• T3: Tumor >50 mm in greatest dimension. T3 tumors should be evaluated for neoadjuvant therapy; re-stage clinically after neoadjuvant treatment to determine surgical approach.
• T4a: Extension to the chest wall (not including only pectoralis muscle invasion).
• T4b: Ulceration of the skin and/or ipsilateral macroscopic satellite skin nodules and/or skin edema (including peau d'orange) that does not meet the criteria of inflammatory carcinoma.
• T4c: Both T4a and T4b present simultaneously.
• T4d: Inflammatory carcinoma: erythema and edema (peau d'orange) involving ≥1/3 of the skin of the breast. Clinical diagnosis; biopsy of skin is supportive but not required. Inflammatory breast cancer is at minimum Stage IIIB. Standard treatment is neoadjuvant chemotherapy (with HER2-directed therapy if HER2+), followed by modified radical mastectomy, then adjuvant radiotherapy. Breast conservation is contraindicated.

N Descriptors

• NX: Regional lymph nodes cannot be assessed (e.g., previously removed).
• N0: No regional lymph node metastasis.
• N1mi: Micrometastasis: tumor deposit >0.2 mm and/or more than 200 cells, but none >2.0 mm in lymph node.
• N1: Metastasis to movable ipsilateral Level I, II axillary lymph node(s).
• N2a: Metastasis in ipsilateral Level I, II axillary lymph nodes that are clinically fixed or matted.
• N2b: Metastasis only in clinically detected ipsilateral internal mammary lymph node(s), in the absence of axillary lymph node metastases.
• N3a: Metastasis in ipsilateral infraclavicular (Level III axillary) lymph node(s), with or without Level I, II axillary node involvement.
• N3b: Metastasis in ipsilateral internal mammary lymph node(s) with axillary lymph node metastasis.
• N3c: Metastasis in ipsilateral supraclavicular lymph node(s).

M Descriptors

• M0: No clinical or radiographic evidence of distant metastasis.
• cM0(i+): No clinical or radiographic evidence of distant metastasis, but deposits of molecularly or microscopically detected tumor cells in circulating blood, bone marrow, or other non-regional nodal tissue ≤0.2 mm in a patient without symptoms or signs of metastasis.
• M1: Distant detectable metastasis as determined by clinical and radiographic means and/or histologically proven distant metastases greater than 0.2 mm.

Stage Groups