What is the TNM (Tumor, Node, Metastasis) staging for a patient with a BI-RADS (Breast Imaging-Reporting and Data System) 4A mass less than 1cm in its widest diameter, without evidence of axillary lymphadenopathy or distant metastasis?

TNM Staging for BI-RADS 4A Breast Mass <1cm

For a BI-RADS 4A breast mass measuring less than 1cm in widest diameter without axillary lymphadenopathy or distant metastasis, the TNM staging would be T1a N0 M0, which corresponds to Stage IA breast cancer. 1

T Descriptor Classification

• A tumor less than 1cm (≤10mm) in greatest dimension is classified as T1a according to the American Joint Committee on Cancer staging system 1
• The T1 category is subdivided based on size: T1mi (≤1mm), T1a (>1mm but ≤5mm for microinvasive, or ≤10mm for invasive), T1b (>5mm but ≤10mm), and T1c (>10mm but ≤20mm) 1
• Since your mass is described as "less than 1cm," this falls into the T1a category if it represents invasive carcinoma 1

N Descriptor Classification

• No axillary lymphadenopathy clinically translates to N0 (no regional lymph node metastasis) 1
• This can be designated as cN0 (clinical) prior to pathologic confirmation, or pN0 (pathological) after surgical evaluation 1
• The absence of palpable or imaging-evident lymph node involvement supports the N0 classification 2

M Descriptor Classification

• No distant metastasis corresponds to M0 classification, indicating no clinical or radiographic evidence of distant metastatic disease 1
• This is determined through appropriate staging workup including imaging studies 3

Overall Stage Grouping

• The combination T1a N0 M0 defines Stage IA breast cancer according to the American Joint Committee on Cancer staging system 1
• This represents early-stage disease with the most favorable prognosis among invasive breast cancers 1

Important Clinical Caveat

• BI-RADS 4A indicates suspicious findings requiring biopsy, but does not confirm malignancy - the TNM staging above assumes pathologic confirmation of invasive carcinoma 1
• If biopsy reveals ductal carcinoma in situ (DCIS) rather than invasive disease, the classification would be Tis (carcinoma in situ) N0 M0, which is Stage 0 disease 1
• Final pathologic staging may differ from clinical staging based on surgical pathology findings, including more precise tumor measurement and lymph node evaluation 3, 4