Seroma (fluid buildup)

This page was reviewed under our medical and editorial policy by

Daniel Liu, MD, Plastic and Reconstructive Surgeon

This page was reviewed on February 8, 2022.

Seroma is a potential complication following breast cancer surgery that affects up to 51 percent of women who have a mastectomy or axillary (armpit) lymph node dissection.

What is seroma?

After breast cancer surgery, fluid may collect where tissue was removed. This swelling is called a seroma. It may resolve on its own over time, or it may need to be drained. Seromas may be uncomfortable and lengthen the patient's recovery time, but they aren’t cancerous.

What causes a seroma?

Seromas are the most common complication of breast cancer surgery. Serous fluid, the clear portion of blood (serum), and lymphatic fluid may build up under the skin in the spaces where tumors, surrounding tissue and axillary lymph nodes were cut out. Seromas may also form in the abdominal region if tissue is taken from there for use in breast reconstruction.  

Seromas may form after a lumpectomy or mastectomy, as well as following the removal of neighboring lymph nodes, breast reconstruction, and other types of surgery. They may take weeks or months to resolve.

Health experts believe a woman's body responds to the trauma of surgery by releasing serous fluid that probably comes from the lymphatic system. Other experts say the fluid in a seroma represents a mix of lymph and serum.

During surgery, doctors may place tubes in the patient's wound to drain off excess fluid. Seromas often result after these drains have been taken out. Although the body generally tends to reabsorb this fluid, sometimes the care team may need to drain it with a hypodermic needle or replace a drainage tube.

Seroma risk factors

Why seromas develop isn’t clear. Suspected risk factors include:

  • Removal of drain tubes from wounds too soon after surgery
  • Use of low-vacuum drains
  • Use of electrocautery to make skin flaps to close over the wound site
  • Early or excessive movement of the shoulder following surgery

According to research published in the Journal of Breast Cancer and Molecular and Clinical Oncology:

  • The size of the surgical area and surgical techniques have been cited as likely contributors to development of a seroma, as have longer surgeries.
  • Radical mastectomies have a higher rate of seromas than simple mastectomies, as do modified radical mastectomies compared with breast conservation surgery (lumpectomy).
  • Seromas were found to occur less often in modified radical mastectomy patients who had immediate breast reconstruction than in those who didn’t.
  • The removal of axillary lymph nodes from under the arm along with breast tissue also heightens risk.

To a lesser extent, inadequate pain relief and use of neoadjuvant chemotherapy have been associated with seromas.

Heavier body weight and higher body mass index are probable risk factors, and perhaps high blood pressure (hypertension). But no confirmed association with seromas following breast cancer surgery has been found regarding:

  • Breast size
  • Tumor location, size, grade, disease stage or hormone receptor status
  • Axillary lymph node status
  • Diabetes
  • Anemia
  • Smoking

Seroma symptoms

Symptoms that signal seroma drainage may need to be done include:
  • Tight skin over the seroma (this could cause problems with healing)
  • Discomfort or pain
  • Restriction of shoulder motion
  • Red, hot skin covering the seroma (this could indicate infection)

Alert the care team if any of these symptoms occur.

Seroma treatment

Small seromas often disappear over time, but long-lasting ones can be troublesome. If a seroma cannot be easily felt through the skin, its dimensions may be determined through ultrasound or a computed tomography (CT) scan.

Seroma aspiration

The fluid in persistent or large seromas may be removed with a hypodermic needle (in a procedure called aspiration), but the fluid may recur. Repeated aspirations raise the risk of infection.


To resolve persistent seromas, the doctor may inject an irritant into the cavity that was formed by tissue removal. This procedure, called sclerotherapy, aims to promote healing by closing up the empty space. Recurrent seromas may require replacement of a drainage tube or, less commonly, surgical drainage.

Seroma prevention

Other seroma treatments are preventive, and may include:

  • Suction drains that reduce the amount of draining liquid
  • Temporary immobilization
  • Compression garments
  • Steroids

Techniques used during a mastectomy and lymph node removal that reduce the empty or dead space formed by tissue loss are thought to help lower the risk of developing a seroma.

Steroids are sometimes used to reduce the inflammatory response to surgery that’s thought to lead to seromas. Research published in the World Journal of Surgical Oncology notes that putting steroids into the surgical wound after breast reconstruction or the first day after a mastectomy with sentinel lymph node biopsy has been shown to cut the risk of seroma development. But a dose of steroids before mastectomy or after mastectomy with axillary lymph node removal doesn't seem to change the odds, researchers found. The use of steroids may also raise the risk of bacterial infection of seromas.

Seroma complications

Potential complications may include:

  • The seroma may swell and ooze fluid from the surgical site.
  • It may reoccur (when fluid refills the space). This isn’t typical, and it requires aspirations to be repeated until it resolves. In some cases, repeated aspirations can promote recurrence.
  • Some seromas become infected, though this is a relatively rare outcome. The infection is treated with antibiotics. The incidence of infection among breast cancer surgery is estimated as ranging from 3 percent to 15 percent, according to a World Journal of Surgical Oncology study.
  • It can create an abscess or become a life-threatening condition called sepsis.
  • Some become calcified or develop a fibrous exterior or capsule and may need to be removed surgically.

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