PURPOSE: To determine whether there are any mammographic and ultrasono
graphic (US) features of epidermal inclusion cysts of the breast, incl
uding heterogeneous microcalcifications, that may be used to preclude
unnecessary biopsy. MATERIALS AND METHODS: Clinical history and imagin
g findings in 15 patients who had undergone surgical excision of an ep
idermal inclusion cyst were reviewed. RESULTS: In 11 patients, imaging
findings of an epidermal inclusion cyst were noted, including 10 pati
ents with mammographic findings, one with US findings only, and seven
with mammographic and US findings. The most common mammographic findin
g (in nine of 10 patients) was an isodense to high-density mass with a
circumscribed margin; three circumscribed masses had multiple associa
ted heterogeneous microcalcifications. In the seven patients with corr
esponding US findings, a circumscribed hypoechoic mass with through tr
ansmission was depicted. An additional US feature in six patients was
extension of the mass into the dermis. CONCLUSION: Biopsy may be deeme
d unnecessary if the characteristic US and physical examination findin
gs are present, even in the case of a cyst with heterogeneous microcal
cifications.