A 29-year-old nulligravid woman presents to the nurse practitioner with a chief concern of a lump in her breast. On clinical exam, the NP detects a 2 cm x 1 cm nontender, smooth, round, rubbery, mobile mass in the upper outer quadrant of the patient’s right breast. The NP understands this mass is most likely which of the following?

Choice A reason: Carcinomas are typically hard, irregular, immobile, and may be associated with skin changes or nipple retraction. While breast cancer must always be ruled out, the described mass lacks the suspicious features of malignancy. Choice B reason: A clogged duct is usually painful and associated with lactation. It presents as a tender, localized area of swelling and is not typically rubbery or mobile. This patient is nulligravid and not lactating, making this diagnosis unlikely. Choice C reason: Fibroadenomas are common benign breast tumors in young women. They are typically smooth, round, rubbery, mobile, and nontender. The location in the upper outer quadrant and the described characteristics strongly suggest a fibroadenoma. Choice D reason: Duct ectasia involves dilation of the milk ducts and may present with nipple discharge, tenderness, or inflammation. It is more common in older women and does not typically present as a discrete, mobile mass.