PURPOSE: To determine whether there are any mammographic and ultrasonographic (US) features of epidermal inclusion cysts of the breast, including heterogeneous microcalcifications, that may be used to preclude unnecessary biopsy. MATERIALS AND METHODS: Clinical history and imaging findings in 15 patients who had undergone surgical excision of an epidermal inclusion cyst were reviewed. RESULTS: In 11 patients, imaging findings of an epidermal inclusion cyst were noted, including 10 patients with mammographic findings, one with US findings only, and seven with mammographic and US findings. The most common mammographic finding (in nine of 10 patients) was an isodense to high-density mass with a circumscribed margin; three circumscribed masses had multiple associated heterogeneous microcalcifications. In the seven patients with corresponding US findings, a circumscribed hypoechoic mass with through transmission was depicted. An additional US feature in six patients was extension of the mass into the dermis. CONCLUSION: Biopsy may be deemed unnecessary if the characteristic US and physical examination findings are present, even in the case of a cyst with heterogeneous microcalcifications.