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. A seroma may show on follow-up imaging studies after treament (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 liklihood 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 quite common following radiation therapy.
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' downard, 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 casued by dying or injured cells can also contribute to accumulations of serum fluid.
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.
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 liklihood 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 liklihood of seroma seems to be the extent of the surgery.
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.
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 aneasthesia 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 immobilzation 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.
Other studies regarding risk of seroma following breast cancer surgical treatment have looked at preexistent 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)
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.