1156 – Giant epidermoid cyst in the breast as a differential diagnosis of locally advanced neoplasia: are we aware of this entity?

Abstract

Introduction: Epidermal inclusion cysts are benign, subepidermal, encapsulated, keratinous nodules of the follicular
infundibulum. They are the most prevalent cutaneous cysts and can develop in any region of the body. They can grow
slowly, be asymptomatic, and persist for years. In the breast, they are extremely rare, infrequently reported, and prone to
complications such as infection, rupture, and malignant changes.
Case report: A 69-year-old woman presented with a 40-year history of a lesion in her left breast, characterized by slow, progressive growth and a significant increase over the last year. On physical examination, a solid-cystic nodule was observed
in the upper outer quadrant of the left breast, measuring 15×13 cm, with a point of fluctuation on palpation, superficial
telangiectasias, cutaneous hyperemia, without local heat, thin overlying skin, and an area of rupture with citrine exudate; the right breast showed no palpable changes or lymphadenopathy. Breast ultrasound revealed a solid, hypoechoic
nodule with irregular contours and calcifications, measuring 12×10.8 cm; axillary lymph nodes had a normal appearance (BI-RADS 4). Mammography was not performed due to the risk of lesion rupture. Core biopsy was performed, and
histopathology revealed keratin laminae. Surgical excision was performed for diagnosis and treatment. A large amount
of sebaceous material with a fetid odor, consistent with the contents of an epidermoid cyst, was removed. The cavity was
irrigated, and complete capsulectomy was performed. The patient remains under outpatient follow-up, without signs of
inflammation or recurrence.
Discussion: The diagnosis of epidermoid cyst is primarily clinical, and complementary examinations are generally unnecessary. In this report, a giant breast nodule with atypical clinical presentation suggestive of malignancy was observed. In
addition, ultrasound revealed findings suggestive of a BI-RADS 4 lesion, raising diagnostic suspicion. Surgery was chosen
for histopathological confirmation and definitive treatment. Therefore, epidermoid cysts are an important entity in the
differential diagnosis and treatment of nodular breast diseases.
Ethics: Research Ethics Committee Aproval (CAAE 83101524000005553).