SONOGRAPHIC FEATURES OF MAMMARY OIL CYSTS

Mammographic lesions that are pathognomonic for oil cysts require no f urther evaluation. Oil cysts, however, may first be discovered by ultr asonography. Between 1988 and 1995, we performed sonography of 26 oil cysts in 15 patients. Sonography was used to evaluate a palpable findi ng when an oil cyst was not initially perceived on the mammogram (47%) or as an initial evaluation of a palpable lump (33%); in addition, oi l cysts were Identified incidentally in 20% of cases. Retrospective re view showed that the sonographic appearance of oil cysts is highly var iable; only 8% mimic simple apocrine cysts. Twelve percent mimic an in tracystic mass. Most have smooth walls (88%), are hypoechoic (65%), an d have neither enhancement or shadowing (50%). The sonographic appeara nce of oil cysts can be suggestive of a pathologic lesion such as an i ntracystic carcinoma. Unnecessary biopsy can be avoided using directed mammography.