Figure 1 Ectopic breast tissue Show full caption (A) Skin-coloured tumour in the left axilla of a 14-year old girl. (B) Histological examination showed slightly hyperplastic glandular tissue without cytological atypia within the reticular dermis and fatty tissue (haematoxylin and eosin staining, original magnification ×20; inset: haematoxylin and eosin staining, original magnification ×100). (C) The glandular epithelium showed positive reaction for oestrogen and progesterone receptors in the immunohistochemical analysis (progesterone staining, original magnification ×200). (D) An MRI scan showed extensive axillary breast tissue (arrows) without connection to the eutopic breasts.

A 14-year-old girl presented with progressively growing bilateral painful axillary tumours ( figure A ). Histopathology showed slightly hyperplastic glandular tissue without cytological atypia within the reticular dermis and fatty tissue ( figure B ). The glandular epithelium stained positive for oestrogen and progesterone receptors ( figure C ), which led to the diagnosis of ectopic breast tissue. An MRI scan showed extensive axillary breast tissue without connection to the eutopic breasts ( figure D ). Ectopic breast tissue occurs in 2–6% of the general population, mainly after incomplete regression along the milk-line. Complete excision was done in our patient because she complained of pain and cosmetic disturbance, and because of the increased risk of primary ectopic breast carcinoma. Ectopic breast tissue should be considered in clinical differential diagnosis of tumours along the milk-line. Histological examination is required to rule out malignancy and in case of a wait-and-see approach, regular breast cancer screening is mandatory.