A 22 year-old woman presents with a firm breast mass. What is the most likely diagnosis?

The most likely diagnosis for a firm breast mass in a 22-year-old woman is fibroadenoma. These benign tumors are most prevalent in women in their late teens to early 30s and are characterized by being well-circumscribed, firm, and often mobile upon examination. Fibroadenomas are composed of glandular and stromal tissue, which contributes to their solid, rubbery consistency.

Typically, risk factors associated with fibroadenomas include being younger, as is the case here, and they may also be stimulated by hormonal influences, which is why they can sometimes increase in size during pregnancy or hormone therapy. The demographics and characteristic nature of the mass align well with this diagnosis, making fibroadenoma a common and anticipated finding in such presentations.

Breast fat necrosis, while also a consideration in certain contexts, usually occurs due to trauma or surgery and might present as an irregular mass. Fibrocystic changes are more common in women in their reproductive years but often present with multiple cysts rather than a single firm mass. Intraductal papilloma typically presents with nipple discharge and may not appear as a palpable mass unless significant in size. Given the age, presentation, and characteristics of the mass, fibroadenoma stands out