A seroma is a buildup of serous fluid that collects beneath the surface of the skin, most often developing after a surgical procedure. This fluid is composed of blood plasma and lymphatic fluid that leaks into the empty space created when tissue is removed or disrupted during an operation. Seromas are a common postoperative occurrence, especially following extensive procedures like mastectomies or large body contouring surgeries. They are generally considered benign, and many small seromas resolve on their own as the body reabsorbs the fluid over time.
Identifying the Seroma’s Visual Appearance
The most noticeable sign of a seroma is localized swelling or a visible lump that appears near or directly beneath the surgical incision site. This swelling typically presents as a dome-shaped or bulging mass, resembling a large cyst just under the skin. The size of the collection can vary significantly, ranging from a small, barely perceptible bump to a prominent bulge that causes the skin to stretch and become taut. Seromas usually appear about seven to ten days after the operation.
In an uncomplicated seroma, the skin overlying the mass usually retains its normal color and texture. While the skin may sometimes appear slightly pale due to the underlying pressure, it does not typically show deep discoloration or intense redness. The fluid itself is characteristically clear, pale yellow, or straw-colored, which helps distinguish a simple seroma from other types of postoperative fluid collections.
What a Seroma Feels Like to the Touch
The physical sensation of a seroma reflects the presence of free-moving fluid under the skin. When gently pressed, a seroma feels soft, “squishy,” and “fluctuant,” similar to the consistency of a water balloon or soft gelatin. The mass is generally mobile, meaning the fluid inside can sometimes be felt shifting or moving when pressure is applied to one side.
A simple seroma is usually non-tender or only causes mild soreness when touched. This soft, yielding quality distinguishes it from the firmness of scar tissue or a solid mass. In rare instances, a seroma that has existed for a prolonged period may begin to calcify, resulting in a hard, fixed lump that no longer has the characteristic fluid-filled sensation.
Differentiating Seromas from Other Post-Surgical Collections
Distinguishing a seroma from a hematoma or an abscess is important because each requires a different approach to care. A hematoma, which is a localized collection of blood, often presents with distinct visual differences. Unlike the typically normal skin color over a seroma, a hematoma causes dark skin discoloration, often appearing as deep purple, blue, or black bruising (ecchymosis).
A hematoma is often firmer and denser to the touch than a seroma because clotted blood is more solid than serous fluid. An abscess, which is a collection of pus caused by a bacterial infection, has the most concerning visual presentation. Abscesses are usually accompanied by intense, spreading redness (erythema) of the overlying skin, and the area is exquisitely tender and warm to the touch.
The fluid collection in an abscess is not simply serum; it contains inflammatory cells and bacteria. If an abscess drains, the discharge will be cloudy, thick, and often foul-smelling, which is markedly different from the clear, pale fluid of an uncomplicated seroma. The presence of systemic symptoms, such as a fever, also strongly suggests an infection rather than a simple fluid accumulation.
Warning Signs and When to Seek Immediate Medical Attention
While many seromas are harmless and resolve naturally, specific changes in their appearance or the surrounding area indicate a potential complication, such as infection, and require prompt medical evaluation. A concerning sign is a sudden, rapid increase in the size of the mass, which may indicate continued fluid accumulation.
The development of intense, throbbing pain, especially when accompanied by changes to the surrounding skin, is a serious warning sign. If the skin over or around the seroma becomes noticeably hot to the touch or develops intense, spreading redness or red streaking, this suggests a developing infection. Any discharge from the incision site that is cloudy, thick, white, or foul-smelling signals that the seroma may have progressed into an abscess.