Background: Isolated axillary lymph node metastases in women without an obvious clinical primary site most frequently originate from the ipsilateral breast and are repeatedly described as occult breast carcinoma. If no primary tumor site can be detected within the whole observation period, ectopic breast carcinoma can be assumed, originating from heterotopic glandular tissue or breast tissue in the axillary fat, extending from the axillary part of the breast. Case Reports: Between 1988 and 1995 we examined and followed up 5 patients with carcinomas found in axillary lymph nodes without clinically detected primary sites. The treatment consisted of 2 local excisions, 3 axillary dissections with 1 limited resection and 1 biopsy of a mammographically suspicious quadrant. In neither case a primary carcinoma was found. Hormone receptor analysis was negative in 3 patients and positive for estrogen in 1 patient. One patient received local radiation, 2 patients were locally radiated in combination with either systemic chemo- or hormonal therapy, the 4th patient received systemic hormonal therapy with tamoxifen over 15 months, and the 5th patient received no additional therapy. Three patients have no evidence of disease at the most recent follow-up 1.5-7 years after diagnosis, 1 patient relapsed locally twice (2 and 27 months after diagnosis) and developed bone metastases, and 1 patient showed relapse at a local site 18 months after diagnosis. Conclusion: The case reports presented indicate that ectopic breast cancer might be a rare variant and should be differentiated from occult breast cancer with lymph node metastases or other primary tumors of the axillary tissue, for example, the rare sweat gland carcinoma. On the assumption of an ectopic breast tumor, axillary dissection should be combined with local irradiation and/or hormonal chemotherapeutic treatment, primary resection of the breast seems to be unnecessary.