Ectopic breast tissue in axillary lymph node.

Benign epithelial inclusions are uncommonly found in lymph nodes, and ectopic breast tissue in axillary lymph nodes is particularly uncommon. The patient is a 48-year-old woman who had an adenoma of the nipple removed 10 years previously. A swollen lymph node with amorphous calcifications in a clustered distribution on mammogram was found in the left axilla. Fine needle aspiration cytology showed only cystic change. Excisional biopsy was performed and microscopic examination demonstrated that the node contained benign mammary epithelial and glandular inclusions, and no evidence of malignancy. Such cases will be increasingly found due to the widespread use of mammography screening and biopsy of axillary sentinel lymph nodes. Ectopic breast tissue in lymph nodes may be mistaken for malignant lesions. It is most important to identify correctly the epithelial inclusions in lymph nodes to prevent an erroneous diagnosis.