Abstract
Accessory breast tissue (supernumerary breast tissue) is due to the absence of regression of the primitive milk lines during embryonic life which extends from the axilla to the groin. It is mostly located in the axilla where it is often confused with the axillary extension of the breast, or any pathological process occurring in armpits. Ectopic mammary glands should not be misdiagnosed as it can potentially undergo the same pathological processes that occur in a normally located breast including benign or malignant breast tumors. We report the case of an intracystic papilloma arising from left axillary accessory breast tissue in a 63-year-old woman. The principal symptom was pain in a palpable left axillary mass without inflammatory signs. Subsequent imaging and histopathologic examination proved it to be a papillary tumor in ectopic breast tissue.