2) A 25-year-old woman presents with a lump in the right breast, noted 2 weeks ago on self-examination. Physical examination findings include a lump in the upper-outer quadrant of the right breast, which is freely mobile, 2×1 cm in size, rubbery in consistency, and with smooth margins. There was no inversion of the nipple, redness, or retraction of the skin, or change in the contour of either breast. What is the diagnostic investigation of choice?
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