Epidermal inclusion cysts of the breast.

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 37-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, fibroadenoma was suspected on the basis of clinical and image findings, but excisional biopsy revealed an epidermal inclusion cyst. The patient in case 2 was a 50-year-old woman with a 2.5-cm lesion in the left breast. Mammography revealed a round, dense, smoothly outlined mass, and sonography showed a well-defined, central hyperechoic mass. . Breast cancer was suspected on the basis of the sonographic findings and the age of the patient, but the resected specimen revealed an epidermal inclusion cyst. Although epidermal inclusion cysts are benign, occasionally they may play a role in the origin of squamous carcinoma of the breast. . Mammographic and sonographic features of an epidermal cyst may mimic a malignant lesion. Malignant change appears to occur more frequently in epidermal inclusion cysts in the mammary gland, compared to common epidermal inclusion cysts, and this may be associated with origination of mammary epidermal inclusion cysts from squamous metaplasia of the mammary duct epithelium. Epidermmoid inclusion cyst of the breast is potentially serious, although such cysts are rare, and differentiation from a malignant or benign breast tumor is required. Excision is probably the most appropriate treatment, and can eliminate the possible risk of malignant transformation.