Seroma (Fluid Buildup)

April 10, 2025

This page was reviewed under our medical and editorial policy by Susan Yost, Ph.D., staff scientist, Department of Medical Oncology & Therapeutics Research, City of Hope^® Cancer Center Duarte

A seroma is one of the common complications after plastic surgery and breast cancer surgery, including lumpectomy, mastectomy and lymph node removal.

This guide is designed to help patients learn more about seroma symptoms and treatment.

What Is a Seroma?

A seroma is a mass or lump of clear fluid (serum) in the body. It may appear after surgery in the empty body cavity where breast tissue was removed. When seromas develop, they tend to appear seven to 10 days after surgery or the removal of a wound drain tube.

Many patients wonder if a seroma is painful. It is possible for a seroma to cause discomfort, although this is not always the case. Smaller seromas are less likely to cause pain. However, the appearance of any abnormality in the breast may cause patients anxiety or stress.

While the exact cause of seromas is not clear, they may be related to:

• An inflammatory reaction in the empty space left after surgery
• An inflammatory reaction to graft tissue introduced to the area
• Disruptions in the normal drainage and flow of blood serum and lymphatic fluids

Several factors are believed to increase a patient’s risk for a seroma. These may include:

• Removing tubes used for wound drainage too soon after surgery
• Too much physical activity immediately after surgery
• Prior radiation therapy to the breast
• Lifestyle-related factors, such as smoking
• Other health conditions, such as obesity and diabetes

Seroma Symptoms

Sometimes, a seroma causes noticeable symptoms. These may include:

• A lump under the skin near the surgery site that may be sore or tender to the touch
• A wave-like motion when touched, indicative of fluid beneath the skin
• Discharge that may be clear or yellow in color

If patients notice any unexpected changes to their body following breast cancer surgery, it is important to seek medical advice.

A seroma is not the only condition that may cause a cyst or lump under the skin, so it may sometimes be mistaken for other, similar conditions, such as the following.

Hematoma: This is an unusual collection of blood that may follow a breast injury. Hematomas usually cause bruises, which are not associated with seromas.

Lymphocele: A collection of lymph fluid that flows into a body cavity, a lymphocele is often similar in appearance to a seroma. Though lymphoceles and seromas are slightly different, they are often identified and treated similarly.

Abscess: This is a collection of pus (white blood cells, dead tissue and germs) that develops when the body tries to fight off an infection. An abscess often causes red, raised skin. In contrast, a seroma is not caused by an infection and does not cause redness. However, it is possible but uncommon for a seroma to become infected and turn into an abscess.

Lymphedema: Caused by a blockage in the lymphatic system, lymphedema may cause swelling, often in one of the limbs. While lymphedema may follow lymph node removal for breast cancer, it is a separate condition from seromas.

Seroma Treatment

Several treatments are available for seroma. Those that are smaller in size, are not causing any pain and not inhibiting movement may be managed at home with regular observation. Often, the seroma will reabsorb into the body on its own, without the need for treatment.

Over-the-counter pain medication may ease discomfort, and a warm compress gently placed on the seroma may aid drainage and reabsorption.

If a seroma is larger, painful or restricting movement, it may be surgically drained with aspiration. Aspiration uses a hollow needle to draw the fluid out of the body.

In very rare cases, an open surgical procedure may be needed to drain the seroma and remove any dead tissue.

Seroma Complications

In some instances, the seroma may return, or refill, after it has been treated. If patients have a seroma that keeps returning, it may need to be surgically removed since multiple needle aspirations may increase the risk of infection.

It is also possible that a seroma may become infected, either by itself or after the aspiration procedure.

Patients should let their doctor know right away if they experience any of these signs of seroma infection:

• Redness or pain near the seroma
• Fever
• Increased heart rate or blood pressure changes
• Discharge from the seroma, which may be white or red, and have an odor
• An opening developing at the suture site