Between 1960 and 1985, 31 patients presented to Institut Curie with isolated axillary lymphadenopathy, of probable metastatic origin from the breast, but without clinical or radiological evidence of a breast tumor and no other primary tumor. The mean age was 54.6 years (range 39-79 years). Histological diagnosis was obtained by axillary surgery (22 cases), drill biopsy (6 cases), and cytology (3 cases). All slides were reviewed for the present study. Treatment consisted of axillary surgery followed by radiotherapy in 22 patients, radiotherapy followed by axillary surgery in 6 patients, radiotherapy followed by modified radical mastectomy in one patient, and radiotherapy alone in 2 patients. Systemic adjuvant treatment was given to 11/31 patients. The median follow-up was 9 years (range 2-26 years). Eight recurrences have appeared. Four patients recurred in the breast only (mean time to relapse: 112 months, range 63-162 months). The four other patients recurred both in breast and/or axilla (mean time to relapse: 23 months, range 7-46 months). Nine patients have developed distant metastases, of whom three also had locoregional recurrence. Among the 11 patients who had had systemic treatment, 5/11 had recurrence or metastases. The overall 5 and 10 year actuarial survival rates were 76 and 71%, respectively. The metastasis-free 5 and 10 year actuarial survival rates were 73 and 71%, respectively. Axillary metastases without clinical or radiological evidence of a primary breast tumor represents a discrete clinical entity, the prognosis of which appears to be better than that of clinical invasive breast cancer with associated lymph node involvement.(ABSTRACT TRUNCATED AT 250 WORDS)