Seventy-four breast cancer patients, who had undergone outpatient excisional biopsy followed by radical mastectomy, were divided into three groups according to the types of intramammary cancer residuals: no cancer residuals--45 patients, noninvasive cancer residuals--15, and invasive cancer residuals--14. The invasive cancer residual group included nine patients with axillary metastasis and showed a significantly higher rate of five-year recurrence (8/14) than the other two groups. In some of the patients with invasive cancer residuals, the lesions were more advanced and aggressive by nature. Histopathologically, invasive cancer residuals closely correlated to the nondesmoplastic infiltrating tumor border, and noninvasive cancer residuals to intraductal cancerous spread. Most intramammary cancer residuals were found close to the wounds made by biopsy.