The Incidence of Metastatic Internal Mammary Node Involvement inPatients with T1 Breast Cancer

Background : It has been recommended that breast cancer patients without clinical involvement of the axilla routinely undergo sentinel node biopsy to obtain important information about the status of the axillary nodes. However, positive internal mammary nodes (i.m.n.) have been documented in patients with histologically negative axillary lymph nodes. The aim of this study was to determine whether an i.m.n. could be the first lymph node to receive malignant cells from a breast tumor. Patients and methods : The incidence of i.m.n. metastasis was examined retrospectively in patients with T1 breast cancer. From 1965 to 1991,74 patients (mean age : 48 years) with T1 breast cancer underwent Halsted mastectomy with i.m.n. dissection at Niigata University Medical Hospital. The i.m.n. dissection included the internal mammary vessels and i.m.n. from the 2nd to the 4th intercostal space. Pathologic specimens were examined by hematoxylin and eosin staining. Results : The incidence of i.m.n. metastases was 12%. Among 5 patients in whom only one tumorpositive lymph node was identified, all had a positive axillary node. Conclusion : These results suggest it is highly unlikely an i.m.n. is the first lymph node to receive malignant cells from a breast tumor.