Background: Several authors have questioned the need for axillary lymph node dissection in T1a breast cancer (primary tumors 5 mm or less in diameter), although current practice typically includes routine axillary lymph node dissection.
Study design: We retrospectively reviewed the records of 2,242 breast cancers in our tumor registries from 1987 to 1994. The incidence of axillary lymph node metastases was determined according to primary breast cancer size. The objective was to determine the need for axillary lymph node dissection in T1a breast cancers, and our data included 74 T1a cancers. Axillary lymph node dissection was performed in 66 of these patients.
Results: Axillary lymph node metastases were found in 3 of 66 cases (4.5 percent). We also reviewed several other institutional series of T1a breast cancers and found no statistical difference in the reported axillary lymph node metastases and our data (p < .10). The combined single-institution data included 256 T1a breast cancers and had a 3.9 percent incidence of axillary lymph node metastases. The Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute published data statistically different from ours. From 1977 to 1982, 339 T1a lesions had a 21 percent incidence of axillary lymph node metastases (p < .005), and from 1983 to 1987, 1,491 T1a lesions had an 11 percent metastatic rate (p < .001). We believe that the SEER data is flawed, because SEER results do not require histologic confirmation of axillary lymph node status.
Conclusions: We believe the single-institution rate of 3.9 percent axillary lymph node metastases in T1a breast tumors results from state-of-the-art breast cancer screening and detection of earlier and smaller lesions. Our data support abandoning routine axillary lymph node dissection in T1a breast cancer.