Hematomas can absolutely last for years, though the ones that do are not ordinary bruises that simply refused to fade. Most hematomas reabsorb within a few weeks as the body breaks down trapped blood and clears the debris. When that cleanup process stalls or is overwhelmed, a hematoma can become a chronic, self-sustaining problem that persists for months, years, or even decades. The reasons range from the body walling off the blood collection in fibrous tissue to calcification that turns a fluid-filled pocket into something closer to bone.
Why Most Hematomas Disappear and Some Do Not
A typical hematoma forms when blood leaks out of damaged vessels and pools in tissue. Within days, the body sends immune cells to digest the spilled red blood cells, and the hemoglobin inside them passes through a series of chemical changes. That progression is what gives a bruise its familiar color shifts from dark purple to green to yellow before vanishing. On MRI, radiologists can actually track these stages: fresh blood looks different from blood that is hours, days, or weeks old because the hemoglobin transforms from one chemical form to another before eventually breaking down into iron-storage compounds like ferritin and hemosiderin.1PubMed. MR appearance of hemorrhage in the brain
The trouble starts when a hematoma is too large for the body’s cleanup crew to handle, when it sits in a location with poor blood flow, or when something keeps feeding it with fresh bleeding. In those cases, instead of dissolving, the hematoma becomes walled off. The body lays down a capsule of scar-like tissue around the blood collection, essentially quarantining it. That capsule can keep the hematoma stable for a long time, but it can also set the stage for the hematoma to grow.
Chronic Expanding Hematomas in Soft Tissue
One of the most striking examples of a hematoma lasting years is the chronic expanding hematoma, a condition first described in detail in clinical literature decades ago. These share a characteristic structure: a central mass of old blood surrounded by a layer of granulation tissue (the body’s wound-repair tissue, rich in tiny new blood vessels), with a dense fibrous shell on the outside. The cruel irony is that the blood breakdown products irritate the granulation tissue lining, which causes those fragile capillaries to leak more blood into the cavity, which irritates the lining further.2JAMA. Chronic Expanding Hematomas: A Clinicopathologic Entity The result is a self-perpetuating cycle: the hematoma feeds itself.
Chronic expanding hematomas have been documented in the thigh, buttock, chest wall, shoulder, and other soft-tissue locations. They can grow slowly over years, sometimes reaching impressive sizes before anyone realizes what is happening. A person might notice a gradually enlarging firm lump and assume it is just scar tissue from an old injury, which is partly why these hematomas are so often diagnosed late.
Chronic Subdural Hematomas
Perhaps the best-studied type of long-lasting hematoma forms between the brain and its outer covering. A chronic subdural hematoma typically begins after a relatively minor head bump, sometimes so trivial the person does not remember it. Blood slowly collects in the space between the brain’s membranes, and over weeks to months, the body forms membranes around the collection. Those membranes contain abnormally fragile new blood vessels, and the combination of continued small bleeds from those vessels, increased fluid seeping through the membrane walls, and trapped cerebrospinal fluid causes the collection to grow rather than shrink.3PubMed Central. Chronic subdural hematoma
The biology behind this persistence is now fairly well understood. Inflammation drives the growth of new blood vessels within the membrane walls, but those vessels are structurally weak. At the same time, the body’s clot-dissolving processes are overactive in these membranes, so any clot that tries to seal a leak gets broken down before it can do its job.4PubMed Central. Pathophysiology of chronic subdural haematoma: inflammation, angiogenesis and implications for pharmacotherapy You end up with vessels that bleed easily and clots that dissolve too fast, a recipe for a hematoma that hangs around indefinitely.
This condition is most common in older adults, partly because the brain shrinks slightly with age, leaving more room for blood to accumulate before symptoms appear. Symptoms, when they do show up, can be subtle: headaches, confusion, unsteadiness, personality changes. Because the initial injury may have happened weeks or months earlier, neither the patient nor the doctor always connects the dots right away.
When Blood Turns to Bone
Some hematomas do not just persist as fluid collections; they harden. Calcification happens when the body fails to reabsorb the trapped blood and instead deposits calcium into it, essentially converting a pocket of old blood into something resembling bone. This is especially well documented in newborns who develop a cephalohematoma, a blood collection under the membrane covering the skull, during delivery. Most of these resolve within a month. Rarely, the blood clots and begins to ossify under the lifted membrane, creating a hard, bony swelling that can last months to years and, if large enough, distort the shape of the skull.5PubMed Central. A calcified cephalohematoma in a 1-month-old infant requiring surgery6PubMed Central. Ossified Cephalhematoma: An Unusual Cause of Calvarial Mass in Infancy
Calcification is not limited to skull hematomas in infants. It can happen in muscle tissue as well. Case reports describe calcified masses forming within muscles like the rotator cuff after old bleeds or tissue death, sometimes mimicking tumors on imaging.7PubMed Central. Supraspinatus Intramuscular Calcified Hematoma or Necrosis Associated with Tendon Tear A calcified hematoma is, in a sense, the body’s plan B: if it cannot clean up the mess, it walls it off and mineralizes it, leaving a permanent but usually inert lump.
The Skin Stain That Outlasts the Hematoma
Even when a hematoma itself has fully resolved, it can leave a lasting mark. As immune cells digest spilled red blood cells, they produce hemosiderin, an iron-storage compound that is essentially insoluble. These hemosiderin granules deposit in the skin and surrounding tissues, creating a brownish, golden, or rust-colored stain that functions like a natural tattoo.8PubMed. Lichen aureus: a hemosiderin tattoo associated with perforator vein incompetence This discoloration can persist for years after the blood itself is long gone, especially on the lower legs where gravity and vein problems concentrate the damage.
Hemosiderin staining is harmless in itself, but it is a common source of worry. People see a persistent dark patch where an old injury was and assume the hematoma is still there. In reality, the blood collection has resolved; what remains is just pigment trapped in tissue. The stain fades extremely slowly because the body has no efficient mechanism for clearing hemosiderin from the skin. Laser treatments can sometimes help, but for many people the discoloration simply becomes a permanent reminder of the original injury.
When a Long-Lasting “Hematoma” Is Not a Hematoma
One of the more unsettling realities about chronic hematomas is that they can look nearly identical on imaging to certain cancers. Soft-tissue sarcomas, a group of malignant tumors that grow in muscle and connective tissue, can mimic hematomas so closely on MRI that even experienced radiologists have trouble telling them apart. Reports in the medical literature describe cases where high-grade sarcomas in the arms or legs were initially diagnosed as post-traumatic hematomas, delaying cancer treatment.9PubMed Central. Soft Tissue Sarcoma Masquerading as Chronic Hematoma: A Case Report and Literature Review
The problem is compounded when there is a history of trauma. A person bumps their leg, notices swelling, and both patient and doctor attribute it to the injury. If the swelling does not resolve over weeks or months, the assumption often is that the hematoma is just slow to clear. But a mass that keeps growing, feels increasingly firm, or causes worsening pain deserves a closer look. The general rule of thumb among orthopedic specialists is that any soft-tissue mass that persists or enlarges beyond the expected healing window should be biopsied rather than simply watched.
What Persistent Hematomas Can Do to Nearby Structures
A hematoma that sticks around does not just sit there passively. Depending on its location, it can compress nerves, block blood flow, or damage surrounding tissue. One well-documented example involves hematomas in the muscles near the hip, particularly the iliacus and psoas muscles. A blood collection in this area can press on the femoral nerve, causing weakness in the leg, numbness in the thigh, and difficulty walking. This complication can develop slowly and insidiously, sometimes presenting weeks after the original bleeding event.10PubMed Central. Iliacus hematoma causing late femoral nerve palsy11PubMed Central. Femoral Neuropathy Secondary to Compression by Spontaneous Iliac Hematoma
Infection is another risk, though an uncommon one. A hematoma is essentially a pool of stagnant blood, which is a good growth medium for bacteria. If bacteria reach the hematoma through the bloodstream or through a nearby wound, the resulting infection can be aggressive because antibiotics penetrate poorly into an encapsulated blood collection. Case reports describe infected hematomas causing significant tissue destruction that required multiple surgeries to control.12PubMed Central. Secondary infection of haematoma following closed acromioclavicular joint dislocation
People at Higher Risk for Persistent Hematomas
Certain groups are more prone to developing hematomas that refuse to resolve. People with bleeding disorders like hemophilia are at the top of this list. Without adequate clotting factors, even minor muscle bleeds can expand and become chronic. If these hematomas are not caught early and treated with clotting-factor replacement, they can evolve into hemophilic pseudotumors, large encapsulated masses of old blood and tissue that can erode into nearby bone and cause serious structural damage.13PubMed Central. Hemophilic Pseudotumors: Diagnosis and Management The emphasis in hemophilia care is on prevention: diagnosing muscle bleeds early and providing prolonged clotting-factor treatment until imaging confirms the hematoma has fully resolved.
People taking blood-thinning medications are another group at elevated risk for hematomas that linger or recur. In the case of chronic subdural hematomas, the relationship between anticoagulants and recurrence has been studied extensively, though the evidence is more nuanced than you might expect. A systematic review found that only one out of multiple studies identified anticoagulant use as a significant factor for rebleeding after chronic subdural hematoma treatment, with the odds roughly doubled in that one study but the overall evidence remaining inconsistent.14PubMed. Anticoagulant and antiplatelet use in seniors with chronic subdural hematoma: Systematic review Antiplatelet drugs like aspirin were not associated with rebleeding in the reviewed studies. So while blood thinners are often blamed for persistent hematomas, the picture is less straightforward than the conventional wisdom suggests.
Other risk factors for slow-resolving hematomas include older age (the immune cleanup system becomes less efficient), liver disease (which impairs production of clotting factors and was associated in a case report with a massive abdominal hematoma following splenic injury that reached 17 centimeters in size15Journal of Trauma and Injury. Very large haematoma following the nonoperative management of a blunt splenic injury in a patient with preexisting liver cirrhosis: a case report), and the location of the bleed itself. Hematomas in enclosed spaces with limited blood supply tend to persist longer than those in well-vascularized areas.
Treatment Options for Hematomas That Will Not Resolve
Management depends heavily on where the hematoma is and what symptoms it causes. For chronic subdural hematomas, the traditional approach has been surgical drainage, either through a small burr hole in the skull or a larger craniotomy. Clinicians generally consider a reduced level of consciousness to be one of the strongest reasons to operate; a survey of neurosurgeons found that a low level of consciousness was considered the most important indication for surgery by about 58% of respondents.16PubMed. Practice variation in the conservative and surgical treatment of chronic subdural hematoma
Not every chronic subdural hematoma needs surgery, though. Conservative management with observation, sometimes with corticosteroids or other medications, is increasingly studied. Research suggests that larger hematoma volume and muscle weakness at the time of diagnosis are factors that predict a patient will eventually cross over from conservative care to surgery.17PubMed Central. Success of conservative therapy for chronic subdural hematoma patients: a systematic review Smaller, less symptomatic collections have a reasonable chance of resolving without an operation.
A newer treatment gaining traction is middle meningeal artery embolization, a minimally invasive procedure where a catheter is threaded through blood vessels to block the artery that feeds the problematic membrane surrounding the hematoma. A major trial published in the New England Journal of Medicine found that adding this procedure to standard treatment cut the risk of treatment failure roughly in half compared with standard treatment alone, with about 16% experiencing treatment failure in the embolization group versus 36% in the control group.18PubMed. Embolization of the Middle Meningeal Artery for Chronic Subdural Hematoma The procedure is increasingly being used both alongside surgery and as a standalone treatment.19PubMed Central. Middle Meningeal Artery Embolization to Treat Chronic Subdural Hematoma
For soft-tissue chronic expanding hematomas, surgical removal of the entire capsule is usually the definitive treatment. Simple drainage often fails because the capsule lining continues to bleed. Calcified hematomas that are not causing symptoms can often be left alone, since they are biologically inert at that point. But if a calcified mass is compressing a nerve, distorting anatomy, or causing cosmetic concern, surgical excision is straightforward.
How Imaging Tracks a Hematoma’s Age
If you have had an MRI for a persistent lump, you may have noticed the radiologist’s report referring to “blood products of various ages” or describing the signal characteristics in language that sounds like a chemistry experiment. That is because the appearance of a hematoma on MRI changes predictably as hemoglobin breaks down. The progression runs from the initial fresh-blood stage through acute and subacute phases, and eventually to a chronic stage dominated by ferritin and hemosiderin, the same iron-storage pigments that cause skin staining.1PubMed. MR appearance of hemorrhage in the brain
Radiologists use these signal patterns to estimate how old a blood collection is, which matters for clinical decisions. A hematoma that shows only chronic-stage blood products has been sitting there for weeks or longer and is unlikely to be actively expanding. Mixed signals, with both fresh and old blood products present, suggest ongoing or recurrent bleeding and often push the clinical team toward intervention. This is also how imaging can help distinguish a long-standing, stable hematoma from one that looks old but is being periodically refreshed with new blood, which is exactly what happens in chronic expanding hematomas and chronic subdural hematomas.
CT scans tell a simpler but still useful story. Fresh blood appears bright white on CT, and as it ages it gradually darkens until a very old hematoma can look the same density as surrounding tissue and become difficult to spot. Calcified hematomas, by contrast, light up brightly because calcium is dense. Ultrasound can also detect hematomas, particularly in soft tissue, and can track whether a collection is shrinking over time, though it gives less detail about the age of the blood products than MRI does.
Hemophilic Pseudotumors
Among the most dramatic examples of hematomas lasting years are hemophilic pseudotumors. These develop in people with hemophilia when a muscle or bone bleed is not adequately treated and evolves into a large, encapsulated mass. The name “pseudotumor” is apt: these lesions can grow to enormous sizes, erode into bone, and compress surrounding structures, all while being entirely non-cancerous. They represent the extreme end of what can happen when the body cannot stop bleeding into a confined space and lacks the clotting machinery to seal the damage.13PubMed Central. Hemophilic Pseudotumors: Diagnosis and Management
Treatment of pseudotumors is complex and usually involves a combination of prolonged clotting-factor replacement therapy and, when conservative measures fail, surgery. Prevention remains the best strategy: catching muscle bleeds early in hemophilia patients and treating them aggressively with clotting-factor infusions until the hematoma is confirmed to be fully resolved on imaging. In parts of the world where access to clotting-factor concentrates is limited, pseudotumors remain a significant source of disability.
For people without bleeding disorders, the takeaway from pseudotumors is a more general one: any hematoma that is not actively shrinking on follow-up visits deserves continued attention rather than a wait-and-see approach that stretches indefinitely. The body is usually good at cleaning up its own messes, but when it fails, early recognition and intervention prevent a manageable problem from becoming a years-long ordeal.