Ultrasonographic demonstration of normal axillary lymph nodes: a learning curve.

High frequency transducers with near field resolution allow visualization of superficial structures in the axilla, such as the lymph nodes, which could not be visualized with older equipment. We have been able to observe normal axillary nodes in 61.5% of 26 women who had histologic correlation of normal lymph nodes at axillary dissection. We studied 663 women with a clinically palpable breast lump using breast and axillary ultrasonography. They were divided into four groups. The first group consisted of all women who had undergone surgery and had histologic correlation of axillary nodes. The second, third, and fourth groups were made up of three consecutive series of 221 women examined. Women from group one were included in groups two, three, and four. A steep learning curve of 7.1 to 41.9 to 64.7% was observed in the detection of normal axillary nodes, suggesting that these appearances can be recognized easily.