Stage IA Breast Cancer (T1c N0 M0)
This is a Stage IA breast cancer, classified as T1c N0 M0 according to the TNM staging system. 1
TNM Classification Breakdown
Primary Tumor (T) Classification
- T1c: A 1 cm tumor falls into the T1c category, defined as a tumor >10 mm but ≤20 mm in greatest dimension 1
- The T1 category is subdivided into T1mi (≤1 mm), T1a (>1 mm but ≤5 mm), T1b (>5 mm but ≤10 mm), and T1c (>10 mm but ≤20 mm) 1
Regional Lymph Nodes (N) Classification
- N0: No regional lymph node involvement means the patient is classified as pN0 (pathological) or cN0 (clinical), indicating no regional lymph node metastasis identified 1
- This assumes histological confirmation showing no regional lymph node metastases, which would be designated as pN0 1
Distant Metastasis (M) Classification
- M0: No distant metastases means M0 classification, indicating no clinical or radiographic evidence of distant metastases 1
Overall Stage Grouping
Stage IA is defined as T1 (including T1c), N0, M0 disease. 1
Clinical Implications
Prognosis
- Stage IA breast cancer has an excellent prognosis, with 10-year actuarial freedom from distant recurrence rates of 91-96% for tumors ≤1 cm when lymph nodes are negative 2
- Even for T1c tumors (>1 cm but ≤2 cm), the prognosis remains favorable, though slightly lower than smaller T1a/T1b tumors 2, 3
Important Caveat
- Despite the excellent overall prognosis, approximately 21% of T1 tumors may have occult axillary lymph node involvement even when clinically negative 2
- The risk of lymph node involvement does not significantly differ between tumors ≤1 cm and those 1.1-2.0 cm 2
- Microscopic invasive tumor size is a better predictor of distant failure than macroscopic tumor size, and should be routinely reported 2
Treatment Considerations
- Stage IA disease typically requires breast-conserving surgery with radiation therapy or mastectomy 4
- Sentinel lymph node biopsy should be performed to confirm pathologic N0 status 4
- Adjuvant systemic therapy decisions depend on additional factors including hormone receptor status, HER2 status, patient age, and tumor biology—even in node-negative disease, chemotherapy and/or endocrine therapy should be considered 3