[Paget's disease of ectopic breast]

Paget's disease of the breast is rare, even more so when it occurs in a supernumerary breast since diagnosis is delayed due to lack of exploration and ignorance of the pathology of ectopic breast. Based on an original clinical case, we provide a clinical update concerning ectopic breast and ectopic carcinoma, including Paget's disease.

A 44-year-old woman had complained of pain in the area of her supernumerary breast for several months. The ultrasound examination was normal but the unexplained symptoms led to performance of an excision biopsy of the lesion. This showed strictly intra-epidermal Paget's disease measuring 2mm, without any underlying carcinoma. A wider excision was performed. Follow-up at one year showed no recurrence.

An ectopic breast, present in 6 % of the population, is often ignored, despite being subject to the same diseases as anatomical breasts: it is at the origin of 0.6 % of breast cancers. Paget's disease is a rare in situ adenocarcinoma comprising fewer than 3 % of cases of breast cancer. It is extremely rare in ectopic breast. Ours is only the fourth reported case in the literature. This case is original because of the lack of objective clinical signs. Subjective symptoms such as pain, tingling, burning sensation and pruritus related to the supernumerary breast must be taken into consideration in order to enable early diagnosis of Paget's disease. Exploration by ultrasound and mammography generally appears flawed. Breast MRI may be useful but is not performed routinely. A promising future approach may consist of confocal microscopy screening of all ectopic breasts with areola or nipple patches, since this method enables the visualization of Paget cells and their organization.