Other causes of breast lumps

What are the other causes of lumps?

Various kinds of lumps can develop in the breast. Mothers should see their health-care providers if they have one that does not go away after a week or have other worrying signs. Some lumps are related to breastfeeding. They may be caused by plugged ducts, mastitis, or breast abscesses, for example. Other lumps may develop during breastfeeding but be unrelated. These include cancer. Lumps are often examined using ultrasound, which can distinguish between fluid-filled lumps, like plugged ducts and abscesses, and solid lumps, like mastitis and tumours. Other tests include mammograms, magnetic resonance imaging, and biopsies.

A) Describing breast lumps

There are multiple causes of breast lumps. Please see your health-care providers if you:

  • Have a breast lump that:
    • Does not clear after one week.
    • Is very painful.
    • Is causing breastfeeding problems.
  • Notice redness in the area.
  • Have blood in your milk.
  • Feel unwell.

Lumps may be filled with fluid (cysts) or they may be solid. They may be related to breastfeeding or due to another problem. Any persistent breast lump must be assessed to ensure it is not caused by cancer.

B) Lumps related to breastfeeding

Lumps related to breastfeeding can be caused by:

Galactocoeles are stretched milk ducts caused by a plugged duct or by inflammation. They can contain milk in different stages of being absorbed into the body.

A phlegmon is an abnormal, irregular area of the breast that is infected and milk cannot drain. It is related to an abscess.

A lactating adenoma shows up as a lump in the breast when a mother is pregnant or breastfeeding and is made up of a dense collection of milk tissue. They are most commonly found in the upper, outer part of the breast. Some clear on their own with weaning. Others grow and must be removed by surgery (Barco Nebreda 2016).

C) Other lumps that can develop while breastfeeding

Lumps that may develop while a mother is breastfeeding but are not related to breastfeeding include:

  • Cysts caused by fibrocystic disease
  • Lymph nodes
  • Non-cancerous (benign) tumours such as fibroadenomas and lipomas
  • Phyllodes tumour
  • Granulomatous mastitis
  • Mammary duct ectasia
  • Bleeding into the breast because of trauma
  • Breast cancer

A phyllodes tumour is similar to a fibroadenoma but may become cancerous.

D) Testing

Ultrasound can detect the difference between solid and fluid-filled lumps and is often used to examine breast lumps. Other tests include mammograms, digital breast tomosynthesis (DBT, or 3D mammography), magnetic resonance imaging (MRI), and biopsies.

Please discuss your options with your health-care providers.


Barco Nebreda I, Vidal MC, Fraile M, et al. Lactating Adenoma of the Breast. J Hum Lact. 2016 Aug;32(3):559-62
Geddes DT. Ultrasound imaging of the lactating breast: methodology and application. Int Breastfeed J. 2009 Apr 29;4:4