Epidermal cysts can be located anywhere: on the scalp, face, trunk, neck and limbs. In the article, specialists from the Department of Surgical Treatment Methods and Antitumor Drug Therapy for Breast Tumors at the Mammology Clinic of the Russian Research Center of Radiology present a rare clinical case of a cyst of atypical localization and a literature review aimed at raising awareness of the existence of epidermal cysts in the parenchyma of the mammary gland. This clinical experience is also interesting from the point of view of differential diagnostics between other benign and malignant formations of the mammary gland to choose the right treatment tactics. © 2024 ABV-press Publishing House. All rights reserved.