What are the causes of a breast lump during lactation (breast feeding)?

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Last updated: April 3, 2025View editorial policy

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Differential Diagnosis for Breast Lump when Breastfeeding

  • Single most likely diagnosis
    • Mastitis: This is the most common cause of a breast lump in a breastfeeding woman. Mastitis is an inflammation of the breast tissue, often caused by a bacterial infection. It is characterized by pain, swelling, and redness of the breast, and can be accompanied by fever and chills.
  • Other Likely diagnoses
    • Breast engorgement: This is a common condition in breastfeeding women, where the breast becomes overfull with milk, leading to swelling and lumpiness.
    • Plugged duct: A plugged duct is a blockage of one of the milk ducts in the breast, which can cause a lump and pain in the affected area.
    • Galactocele: A galactocele is a milk-filled cyst that can form in the breast, often as a result of a blocked duct.
  • Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
    • Breast cancer: Although breast cancer is rare in young women, it is essential to consider it as a possible cause of a breast lump, especially if the lump is painless, hard, and fixed in place.
    • Abscess: A breast abscess is a collection of pus in the breast tissue, which can be life-threatening if left untreated. It is often accompanied by severe pain, swelling, and redness of the breast.
  • Rare diagnoses
    • Fat necrosis: Fat necrosis is a rare condition where the fatty tissue in the breast becomes damaged, leading to the formation of a lump.
    • Lipoma: A lipoma is a rare, benign tumor made up of fat tissue, which can occur in the breast.
    • Hamartoma: A hamartoma is a rare, benign tumor-like growth that can occur in the breast, often composed of a mixture of glandular, fibrous, and fatty tissue.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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