Ductal Carcinoma Arising from Ectopic Breast Tissue Following Microcalcification Observed on Screening Mammography: A Case Report and Review of the Literature

Ectopic breast tissue can occur anywhere along the incompletely regressed mammary ridge. Among the various types of breast choristoma, ectopic breast tissue, which has only glandular tissue without a nipple or areola, is most commonly detected in axillary areas. However, ectopic breast cancer is often not detected until significant clinical symptoms have been revealed, or diagnosis is delayed. Furthermore, an examination of ectopic breast tissue tends to be omitted from a screening mammography. Especially, the microcalcifications of ectopic breast tissue are difficult to delineate on mammography. Herein, the authors report a case of ectopic breast carcinoma that showed clustered microcalcifications on screening mammography, and discuss the interpretation and implications of microcalcification in ectopic breast tissue.