Background: The internal mammary lymph nodes (IMN) have received little attention in recent years, yet are a well-documented site of metastasis and a major prognostic factor in early-stage breast cancer.
Methods/results: Ten-year follow-up of the final 195 patients treated by extended radical mastectomy (ERM) in this practice (selected largely on the basis of medial tumor location, and comprising 15% of all patients treated from 1965 to 1978) found IMN+ in 24% of all cases: 36% of AX+ versus 18% of AX- patients (p = 0.0023). In a multivariate analysis, the disease-free survival impact of IMN+ (p = 0.004) was second only to axillary node involvement (p < 0.0005), and surpassed tumor size (p = 0.077). IMN+ was equally frequent for tumors less than, or greater than, 2 cm (24%), and was not significantly related to patient age. Among AX- patients, there was a twofold greater risk of recurrence or death at 10 years for IMN+ than for IMN-. Among T1N0 patients, 19.6% were IMN+.
Conclusions: Failure to consider IMN status in the steadily enlarging cohort of T1N0 breast cancers may result in the undertreatment of a significant proportion of stage I patients. Systemic adjuvant therapy should be considered for T1N0 patients with central or medial tumors.