The most appropriate management of this woman's breast mass is diagnostic ultrasound. Although up to 90% of breast masses are benign cysts or fibroadenomas, neither the history nor the physical examination can definitively rule in or rule out underlying malignancy with accuracy. Therefore, a palpable mass requires further evaluation with either mammography or ultrasonography; in this 29-year-old woman, a diagnostic ultrasound is the most appropriate next step as it is more sensitive than mammography in younger women. Ultrasonography can effectively determine whether the lesion is solid or cystic, delineate its contours, and can help determine whether additional evaluation with biopsy is indicated.

Mammography, whether digital or film, is less sensitive in women younger than 35 years because of increased breast density. Therefore, ultrasonography is the most appropriate initial imaging choice for this patient.

Aspiration biopsy should not be the next step in this young woman at low risk for breast cancer. She has no family or personal history of breast cancer, has no history of thoracic irradiation, and is not obese. Ultrasonography is the most sensitive and noninvasive way to determine whether or not a biopsy is necessary.

There is no need to stop hormonal contraception in a young woman at risk for pregnancy in the absence of neoplasia or a high risk for neoplasia. One of the therapeutic benefits of combined hormonal contraception is a reduction in prevalence of breast cysts. Given the individualized risk stratification for this young woman, with low risk for breast malignancy, it is reasonable to continue her method of contraception until there is definition of the breast mass.

A palpable breast mass requires further evaluation at any age. The history and physical examination are unlikely to rule out malignancy, and a malignant lesion must be ruled out.