Epidermal inclusion cyst of the breast: A case report.

Epidermal inclusion cysts are nonmalignant proliferations of squamous epithelium situated within the dermis. Their presence in the breast is uncommon and presents considerable diagnostic difficulty. This case report aims to elucidate the multimodal imaging findings and differential diagnosis of a rare breast epidermal inclusion cyst, highlighting its capacity to mimic malignant neoplasms. We present a case of a 38-year-old female with a palpable right breast nodule that had progressively increased over a period of 15 years. A clinical examination identified a firm mass in the upper inner quadrant of the right breast. Ultrasound revealed a heterogeneous solid nodule, whilst mammography detected a sizable, well-defined hyperdense mass (BI-RADS 4). Magnetic resonance imaging demonstrated a well-defined nodule with T2/STIR hyperintensity, characterized by a ring-like internal enhancement pattern and restricted diffusion, classified as BI-RADS 4. An ultrasound-guided core biopsy was performed, and histological analysis confirmed the diagnosis of an epidermal inclusion cyst. This case underscores the importance of considering epidermal inclusion cysts in the differential diagnosis of breast cancers with imaging features to avoid unnecessary invasive interventions.