Cholesterol and Cholesterol Epoxides in Nipple Aspirates of Human Breast Fluid¹

In nipple aspirates of breast fluid from nonpregnant healthy women, cholesterol and cholesterol epoxide levels were determined with gas-liquid chromatography and mass spectrometric techniques. Cholesterol levels were found to be elevated above plasma levels averaging 2200 ± 1995 (S.D.) mg/dl and showing progressive increases in mean breast fluid cholesterol levels with advancing age, averaging 187, 1957, and 3554 mg/dl in women of age groups 20 to 29, 30 to 39, and 40 to 49 years, respectively. Cholesterol epoxide was detected in a significant number of women who yielded high levels of breast fluid cholesterol. Cholesterol epoxide has been reported by other workers to have transforming activity for embryo hamster cells and to be carcinogenic in animals. The findings lend support to our hypothesis and observation that the human breast secretes mutagenic and cancer-promoting substances which may have relevance in studies of the etiology of benign breast disease and cancer.