Breast Seroma

Seroma is a pocket of clear fluid which sometimes develops following a surgery.

They are very common after breast cancer surgical treatments, and also axillary surgeries if there has been metastasis and lymph node involvement.

They also occur after breast reduction surgery, breast augmentation surgery, breast biopsy surgery, and basically, any kind of surgery in any part of the body,.

A seroma may show on follow-up imaging studies after treatment (possibly causing some initial concern as a developing ‘lesion’ ), but more commonly they are quite visible and palpable.

Seromas are completely unrelated to ‘cancer cells’ and of no increased risk or concern whatsoever. But, they can complicate and extend the recovery period as the fluid needs to be drained.

Seromas may also increase the likelihood of ‘surgical site infection’ (SSI) , so they do have to be treated and monitored. Seromas are not unique to the breast, but can develop anywhere in the body after any trauma or surgery. They are also seen following radiation therapy.

seroma ultrasound post breast cancer surgery

Dr. Halls Dr. Halls
This ultrasound shows fluid (dark area) in a breast


What causes a seroma?

There are a couple of different ways a seroma could form. Blood is essentially made from a combination of serum (liquid) and red blood cells. Sometimes the red blood cells ‘settle’ downward, causing it to separate from the serum. The serum then collects into a ‘seroma’.

Another way seromas can develop is from ‘leaky’ blood vessels. If there is a tiny tear in the lining of a blood vessel or capillary, this can allow the serum to escape, but not the red blood cells. Inflammation caused by dying or injured cells can also contribute to accumulations of serum fluid.

Seromas often ‘remain’ following a breast hematoma

Seromas are different from breast hematomas, which contains red blood cells, and breast abscesses, which contain pus and are the result of an infection. However, sometimes a seroma can ‘remain’ following the development of a hematoma. The ultrasound image above is likely one of these ‘remnant’ seromas following a hematoma.

How common is a seroma following breast cancer treatment?

There is considerable difference of opinion as to the rate of seroma development, and even more confusion regarding the possible factors, whether treatment parameters or patient characteristics, that might predispose a woman to developing a seroma post surgery. From the available data, one might suggest the overall likelihood of developing a seroma following breast cancer surgical treatment is between 16% and 35%, so, maybe 1 out of every 4 women or thereabouts. There is really no way to predict this, and the only consistent factor influencing the likelihood of seroma seems to be the extent of the surgery.

Factors supposed to influence likelihood of developing a seroma following breast cancer surgical treatments

Many different ideas have been tested to see if they influence the probability of seroma development. While many studies claim to have evidence of increased risk factors in so many different aspects of breast cancer treatment, the only factor which seems to have a consistent and verified bearing on developing a seroma, is the extent of the surgery. A woman who undergoes a modified radical mastectomy (MRM or removal or breast) is thought to be about 2-3 times more likely to develop a seroma than a woman who’s breast cancer is treated with breast conserving surgery (BCS), and this seems logical.

breast seroma xray

Other suggested factors for seroma development: unproven

Many ideas that have been considered as risk factors for developing seroma, from just about every conceivable aspect of the procedure and the patient. Some studies have looked at factors of the blood; anemia, blood transfusion and blood loss during surgery. Others have considered technical aspects of the surgery itself. These include: the kind of scalpel used, the angle of incision, the type of anesthesia used, various aspects of suturing and skin flaps, the use of ‘adhesive glues’, the type and pressure of dressing used, whether the area is immobilized and the amount of time before immobilization is removed (for shoulder surgeries), the length of the operation, the type of drainage (closed suction drain versus static drain, multiple channel vs. multiple holes), or the use of a fibrinolysis inhibitor.

Only the severity of breast surgery has a proven bearing on seroma development

Other studies regarding risk of seroma following breast cancer surgical treatment have looked at pre-existent conditions such as hypertension and diabetes mellitus, and any previous biopsies. Radiation treatment and adjuvant therapies have also been considered. Specific histological features including the size and grade of tumor, hormone receptor status, lymph node status ( positive or negative for breast cancer metastasis), number of lymph nodes removed ( in axillary surgery) have also been considered. Some studies have even considered body-type and general health issues such as the size of the breasts, age, body weight, and smoking. Again, none of the above listed factors have been proven to have any consistent influence on risk of seroma, with the exception of severity of surgery. (MRM vs. BCS)

Treatments of seroma

Seromas will gradually be re-absorbed by the body, and most surgeons view them as an unavoidable nuisance rather than a serious complication. However, this can take many days or even weeks. Sometimes a ‘knot’ of calcified tissue remains after the seroma has dissipated. This calcification may show up on follow-up imaging studies, but is of no health concern whatsoever. However, sometimes the accumulation of fluid in a seroma can be excessive, causing the skin to stretch and to sag. This can be uncomfortable for the patient and prolong the recovery time in hospital. In these situations the seroma might be drained by needle aspiration, but this can take several visits.

Dr. Halls Dr. Halls
I drain seromas with needle aspiration, all the time.

Seromas versus hematoma, is kind-of decided once you aspirate the fluid into a syringe, and see the color. If the fluid is yellow, call it a seroma. If very red, call it hematoma. In-between, call it whatever you want.

Yes, they gradually go away without aspiration. Yes, things get back to normal quicker if they are aspirated.

Q and A

  • Where does seroma fluid come from? Sometimes it’s from a hematoma (bleeding) that separated into blood clot and yellow fluid (serum). Other times, it’s leak of yellow fluid from tissues, “just because”. Because why? I guess something made capillaries leaky. The capillary endothelial cells lining the blood vessels got sick. “how?” Maybe during surgery, the tissues were compressed more than they liked, or their blood supply got a bit dampened.
  • When will seroma go away? Eventually, or sooner if someone will agree to aspirate it. Does it come back? Yes, but usually much smaller the second time.
  • How to avoid a seroma? I believe direct hand pressure on wounds is the best. I believe tissues wounded by surgery, then stitched together, should be not massaged or pushed in different directions. You have to give time, for undisturbed cut tissue edges, to rejoin each other.
  • Are seroma dangerous? No.
  • Are seroma painful? Yes, often they stretch the surrounding tissue, stretching nerve endings, which send complaining signals to the brain, which the brain interprets as pain.
  • .


  1. Boostrom, SY., Throckmorton, AD.,Boughey, JC., Holifield, AC., Zakaria, S., Hosking, TL., Degnim, AC., Incidence of clinically significant seroma after breast and axillary surgery. American Society of Clinical Oncology: Proceedings of 2008 Breast Cancer Symposium.
  2. Pogson CJ, Adwani A, Ebbs SR. Seroma following breast cancer surgery. Eur J Surg Oncol. 2003;29:711–717.
  3. Hashemi, E., Kaviani, A., Najafi, M., Ebrahimi, M., Hooshmand, H., Montazeri, A. , Seroma formation after surgery for breast cancer. World J Surg Oncol. 2004; 2: 44.
  4. Woodworth PA, McBoyle MF, Helmer SD, Beamer RL. Seroma formation after breast cancer surgery: incidence and predicting factors. Am Surg. 2000;66:444–450.
  5. McCaul JA, Aslaam A, Spooner RJ, Louden I, Cavanagh T, Purushotham AD. Aetiology of seroma formation in patients undergoing surgery for breast cancer. Breast. 2000;9:144–148.
  6. Chourmouzi, D., Vryzas, T., Drevelegas, A., New spontaneous breast seroma 5 years after augmentation: a case report. Case Journal, 2009, 2:7126.
  7. Kuroi, K., Shimozuma, K., Taguchi, T., Imai, H., Yamashiro, H., Oshumi, S. Saito, S., Evidence-Based Risk Factors for Seroma Formation in Breast Surgery. Japanese Journal of Clinical Oncology 2006 36(4):197-206
  8. Forouhi P, Dixon JM, Leonard RC, Chetty U. Prospective randomized study of surgical morbidity following primary systemic therapy for breast cancer. Br J Surg 1995;82:79–82

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