For a 25-year-old female with a 2 cm breast mass, what is the modality of choice to further evaluate her condition?

In the evaluation of a breast mass in a young woman, particularly one that is under 30 years old, ultrasound is typically the first-line imaging modality. This is due to the higher density of breast tissue in younger women, which can make mammograms less effective at distinguishing between benign and malignant lesions. Ultrasound is excellent for characterizing breast masses because it can help determine whether the mass is solid or cystic and can provide additional information about its morphology.

Using ultrasound not only aids in diagnosis but can also assist with guiding an aspiration or biopsy if necessary. In contrast, other modalities such as mammography may not provide the clarity needed in younger patients and are generally reserved for certain situations, particularly when a mass is found on physical exam or ultrasound, and there is a need to screen for additional lesions.

Excisional biopsy, while definitive for diagnosis, is more invasive and is usually pursued if imaging raises suspicion for malignancy and when directed biopsy is not possible. MRI is typically reserved for specific cases such as high-risk screening or assessing the extent of known breast cancer rather than initial evaluation of a palpable mass in a young woman.

Thus, for this case, ultrasound stands out as the most appropriate first step in further evaluation, providing safe, accurate,