A case of unilateral accessory axillary breast tissue developed as a subcutaneous nodule unassociated with menstrual periods, pregnancy, or lactation in a 33-year-old parous woman. Histopathologic finding of the nodule revealed lobules of normal breast tissue forming islands of glandular tissue, This case belongs to one of the unusual forms of supernumerary breast tissue characterized by the presence of aberrant gland tissue alone. The literature is briefly reviewed.