The impact of microinvasion on axillary node metastases and survival in patients with intraductal breast cancer. A rational approach to the local treatment of intraductal breast cancer continues to generate considerable debate. However, the finding of an invasive component in intraductal breast cancer is widely regarded as an appropriate indication for axillary node dissection as part of the local treatment and staging of this disease. Despite this view, the natural history of patients with intraductal breast cancer with foci of microinvasion is poorly defined. Between 1965 and 1988, 41 patients with this pathologic finding of intraductal carcinoma with foci of microinvasion were seen at the UCLA Medical Center. Twenty-three patients presented with mammographic abnormalities, while 17 patients presented with a palpable mass. One patient presented with Paget's disease of the nipple. Thirty-three patients underwent axillary node dissection as part of their local treatment. No lymph node metastases were identified. The median follow-up in 37 patients was 47 months. There have been no local recurrences and no deaths from recurrent breast cancer. Intraductal breast cancer associated with microinvasion appears to be an extremely favorable lesion with minimal risk of nodal metastases. 