What are the causes of breast lumps?

Causes of breast lumps include:

  • Changes in the breast (fibrocystic changes): Tiny, fluid-filled sacs and fibrous (rubbery) tissue feel like lumps.
  • Breast cysts: Fluid-filled sacs form when fluid becomes trapped in the milk ducts. Cysts are common in younger people.
  • Fibroadenomas: This benign (noncancerous) lump is the most common breast tumor. Fibroadenomas are most common during a person’s reproductive years.
  • Breast infection: An infection in the breast tissue can cause a lump.
  • Breast cancer: A tumor starts growing in the breast tissue.

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