A 24-year-old woman notes a lump in her right breast for the past month. She is concerned because her sister was diagnosed with poorly differentiated "triple-negative" breast cancer at age 31. Ultrasonography of the breast shows a solid mass. Fine needle aspiration is attempted but no diagnostic cells are obtained. Mammography is performed and there is a single 1-cm density with small clustered calcifications in the right breast but no lesions of the opposite breast. Which of the following is the best course of action for this patient?
Biopsy to obtain tissue from the lesion Continued monthly breast self-examination Genetic testing for BRCA1 mutations Hormonal therapy with tamoxifen