Epidermal inclusion cysts are uncommon in the breast, but the consequences can be severe when these cysts occur in the breast parenchyma. Here, we report two such cases. The patient in case 1 was an 85-year-old woman with a 3-cm palpable mass in the right breast. Mammography revealed a round and smoothly outlined mass, which indicated a benign tumor, and sonography showed an irregularly shaped and heterogeneous hypoechoic mass. Breast cancer was suspected on the basis of the sonographic findings and the age of the patient, but excisional biopsy revealed an epidermal inclusion cyst. The patient in case 2 was a 45-year-old woman with a 9-cm lesion in the left breast. Mammography revealed a round, dense, smoothly outlined mass, and sonography showed a well-defined, central hyperechoic mass. A phyllodes tumor or a giant fibroadenoma was suspected on the basis of clinical and imaging findings, but the resected specimen revealed an epidermal inclusion cyst.