Objectives: To find out whether macroscopic classification of the tumour margin is predictive of axillary lymph node metastases and to identify a combination of clinical and pathological findings by which axillary node status can be predicted accurately in small carcinomas (T1) of the breast.
Design: Retrospective study.
Setting: Municipal referral centre, Japan.
Subjects: All 1003 patients with T1 invasive carcinoma of the breast who had axillary lymph node dissection between January 1970 and December 1996 as part of their treatment.
Main outcome measures: The association between the incidence of axillary lymph node metastases and 10 clinical and pathological factors (age, palpability and size of tumour, macroscopic classification of tumour margin, clinical axillary status, radiating spiculation on a mammogram, histological type, lymphatic invasion, oestrogen and progesterone receptor status) were analysed.
Results: Clinical axillary node status, macroscopic classification of tumour margin, lymphatic invasion, and age of the patient were significant predictors of axillary lymph node metastases (p < 0.01 in each case). Among 47 patients aged 65 or more whose tumours had well-defined margins and with a clinical N0 status in the axillae, the incidence of histological axillary lymph node metastasis was only 6% (n = 3) whereas it was 65% in 57 patients with tumours of ill-defined margins whose axillae were N1 or N2.
Conclusions: Macroscopic classification of tumour margins is an independent predictor of axillary lymph node metastases for patients with small carcinomas of the breast. However, even with combinations of the examined predictors of axillary node metastases, the subgroup of patients at minimal risk of metastasis was less than 5% in T1 breast cancer, whereas three-quarters of the patients had clear axillary lymph nodes. Most patients with T1 breast cancer will need surgical staging of the axillae by methods such as sentinel node biopsy.