There are several potential causes of lumps in the breast, which include cysts and tumors. A cyst can form when fluid builds up in the breast, while a tumor is a solid mass that can be either noncancerous or cancerous.

People of all sexes and genders can develop lumps in the breast tissue. Regardless of whether a person suspects a lump in the breast of being a tumor, a cyst, or something else, they should contact a doctor.

While most breast lumps are not cancerous, some noncancerous lumps also require medical treatment, and it is important for a doctor to rule out a cancerous tumor.

This article looks at breast cysts, tumors, and the differences between them. We also look at diagnosis, cysts and cancer risk, breast changes, breast self-exams, and when to contact a doctor.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

A person undergoing a mammogram to identify a breast cyst or tumor.Share on Pinterest
Helen King/Getty Images

Breast cysts are rounded, fluid-filled structures ranging from very small, to large enough to feel through the skin.

According to Breastcancer.org, around 25% of masses or lumps in the breast are cysts, and most are noncancerous.

People of any age can develop cysts in the breast, but they are most common in females in their 40s. People typically develop multiple cysts, either suddenly, or over a period of time.

Most people do not experience pain from breast cysts, however, it is a possible symptom. Other symptoms include:

  • tenderness in the breast
  • lumps in the breast
  • worsening of symptoms during the menstrual cycle

Types of breast cysts include:

  • Simple cysts: Simple cysts are always noncancerous. These cysts are completely fluid-filled and have no solid mass. The walls of simple cysts are thin and smooth with no irregularities.
  • Complex cysts: These cysts have thick walls and are irregularly shaped. They may contain some solid mass or debris as well as fluid. A doctor may drain some of the fluid to test it for irregularities, to rule out breast cancer.
  • Complicated cysts: These cysts share features of both simple and complex cysts. The walls of complicated cysts are thin and smooth, like those of a simple cyst, and they typically do not contain obvious solid mass. However, they may contain some of the types of debris that doctors typically see in complex cysts.

Experts do not know the exact causes of breast cysts, but research suggests they may be linked to changes in specific hormones, including estrogen and progesterone.

A tumor in the breast is a solid mass, and it can be noncancerous or cancerous.

Noncancerous breast tumors

These tumors are made of abnormal cells, but are benign, and cannot spread to other areas of the body. These are typically harmless, although they can be problematic if they grow large and press on other areas of the body.

Tumors can occur when the process of cell growth to replace old cells goes wrong, and the body forms unnecessary new cells. These excess cells can continue dividing and form a tumor.

Common types of noncancerous breast tumors include:

  • Phyllodes tumor: Most phyllodes tumors are noncancerous, although 1 in 4 is malignant, or cancerous. These tumors begin in the breast’s connective tissue, rather than in the glands or ducts, where most breast cancers start.
  • Fibroadenoma: These are a common type of noncancerous tumor, which develop from connective and glandular breast tissue.
  • Intraductal Papillomas: These noncancerous tumors grow in the milk ducts of the breast and are wart-like. They may cause bloody or clear discharge from the nipple.

Cancerous breast tumors

Breast cancer is a type of cancer that starts with tumors developing in the breast tissue.

If the abnormal cells appear to be cancer cells under a microscope and have not spread to the nearby tissue, doctors refer to it as in situ. When cancer spreads to nearby tissue, lymph nodes, or other areas of the body, doctors refer to it as invasive.

Changes to DNA cause breast cancer, although experts do not know exactly what causes genetic material to change.

Types of breast cancer include:

If a person has a lump in their breast, they should contact a doctor.

Differences between cysts and tumors in the breast can be difficult to determine without medical attention, and some conditions may present differently than the norm.

According to the American Cancer Society and Breastcancer.org, features of breast cysts include the following:

  • They may be painful.
  • They move easily under the skin.
  • They are typically smooth and soft.
  • The symptoms can become better or worse during different phases of the menstrual cycle.

Features of breast tumors include the following:

  • They are typically painless.
  • They do not move when a person prods them.
  • They may have uneven, hard edges.
  • The symptoms do not change depending on the phases of a person’s menstrual cycle.

There are many other symptoms of breast tumors. If a person notices any changes in their breast, they should speak with a doctor.

To diagnose breast tumors and breast cysts, healthcare professionals will often order a diagnostic mammogram and an ultrasound.

If the results of the imaging tests are abnormal, they will then order a biopsy.

Simple cysts do not increase a person’s risk of breast cancer. If a person has complex or complicated cysts in their breast, there is a slight risk that the solid mass in the cyst may contain cancer cells.

Complex and complicated cysts may also increase a person’s risk of breast cancer at a later stage, depending on the results of their biopsy.

Breast changes may be an indication of breast cancer. These can include:

  • a change in shape or size
  • a swelling or lump in an armpit
  • a change to the appearance of the nipple, such as a sunken appearance
  • thickened tissue in the breast
  • a new lump anywhere in the breast
  • fluid discharge from the nipple
  • a change to the breast skin, such as puckering, redness, or dimpling
  • an itchy, red rash around the nipple

According to Breastcancer.org, there are five steps to checking for breast lumps at home. A person should:

  1. Place their hands on their hips and look at their breasts in a mirror. A person should check for any visual changes to their breasts.
  2. Raise their arms above their heads and examine their breasts in the mirror, and again check for visual changes.
  3. Look at the nipples for signs of clear, milky, or bloody fluid leaking out.
  4. Lie down, and use a firm, smooth touch to examine the entirety of each breast, from the collar bone to the top of the abdomen, and from the armpit to the cleavage. A person should move from the nipple in concentric circles to ensure they have felt the whole of each breast.
  5. Perform the same motions to touch and check each part of the breast while sitting or standing.

Learn more about how to perform a breast self-examination here.

An individual should contact a doctor if they:

  • notice any visual changes to the breast, such as puckered skin, redness, size and shape change, or rash
  • feel a lump in their breast or their armpit
  • notice discharge from the nipple

The American Cancer Society outlines the guidelines regarding when people should get a mammogram:

  • Those aged 40–44 years: They have the option of getting a screening once a year.
  • Those aged 45–54 years: People should continue getting a mammogram every year.
  • Those 55 years and older: People this age can get a screening every other year or continue getting a screening every year. They should continue getting mammograms for as long as they are in good health and are expected to live for at least 10 years.

A person may prefer to begin screening sooner if they have a family history of breast cancer.

An abscess in the breast is a pus-filled lump that develops under the skin.

Infection typically causes an abscess, and they most often grow during breastfeeding, however, anyone can develop one.

To treat an abscess in the breast, a doctor may prescribe antibiotics, and may drain the fluid from the lump with a small needle.

Breast cysts are fluid-filled lumps that may occur as a result of changes in hormones. They are sometimes painful, move easily under the skin, and are benign and not usually indicative of cancer.

Symptoms of a breast cyst may become worse or better at certain phases of the menstrual cycle.

Breast tumors are not typically painful, are hard to the touch, and do not move when touched. They also do not change according to phases of the menstrual cycle. Tumors may be cancerous or noncancerous.

Changes to the breast may indicate that a person has breast cancer, such as puckering of the skin, changes to the shape and size of the breast, and a rash or discharge from the nipple.

Anyone with a lump in their breast or under their arm should contact a doctor to check for breast cancer or other conditions that may require treatment.