What Is a Vascular Lesion? Types, Causes, and Care

A vascular lesion is any abnormality involving blood vessels or lymphatic vessels, ranging from a faint birthmark to a deep tangle of malformed arteries. The international medical classification divides them into two broad groups: vascular tumors, which involve abnormal cell growth, and vascular malformations, which are structural errors in how vessels form. That distinction matters because the two behave differently, respond to different treatments, and carry different risks. The term “vascular lesion” is deliberately broad, and understanding what kind you or your child has is the first step toward knowing what to expect.

How Vascular Lesions Are Classified

For decades, vascular lesions were lumped together under vague labels like “hemangioma” or “birthmark,” which made it hard for doctors to communicate clearly or choose the right treatment. The International Society for the Study of Vascular Anomalies (ISSVA) first formalized a classification system in 1996, separating lesions into tumors and malformations based on their biology. A 2014 update retained that basic framework but added many newly identified subtypes driven by advances in genetic testing.¹ The most recent revision continues to use this two-branch system as a landing page, with tumors on one side and malformations on the other.²

The reason this classification matters in practice is straightforward. Vascular tumors are growths: they have cells that multiply, and they may shrink on their own or respond to drugs that slow cell division. Vascular malformations are wiring problems: the vessels themselves are built incorrectly from before birth, and they tend to persist or slowly expand over a lifetime. Confusing the two leads to wrong treatments and unnecessary worry.

Vascular Tumors

Vascular tumors are the lesions most people picture when they hear “vascular birthmark.” They involve actual proliferation of the cells lining blood vessels. The ISSVA groups them by how aggressively they behave: benign, locally aggressive (borderline), and malignant. Most vascular tumors in children are benign.

Infantile Hemangioma

The most common vascular tumor in infancy, infantile hemangioma (IH) typically appears in the first few weeks of life as a red or bluish raised patch, grows rapidly for several months, and then slowly shrinks over years. A hallmark of IH at the cellular level is that the tumor’s endothelial cells express high levels of a protein called GLUT1, which is not found in other vascular tumors or in normal skin vessels.³ This makes GLUT1 a useful diagnostic marker when a biopsy is needed. Research has also shown that these GLUT1-positive cells behave like stem cells in laboratory conditions, which helps explain the tumor’s ability to grow quickly and then involute as the cells change character.⁴

Most infantile hemangiomas need no treatment at all because they resolve on their own. When treatment is warranted, propranolol, a beta-blocker originally used for heart conditions, is now the standard first-line drug. It accelerates shrinkage and is well established for this purpose.⁵

Congenital Hemangioma

Unlike infantile hemangioma, congenital hemangiomas are fully formed at birth and do not go through a postnatal growth phase. They come in three flavors. Rapidly involuting congenital hemangiomas (RICH) start shrinking within weeks, with involution beginning at a median age of about four weeks in one review, and most resolving within the first year.⁶ Even very large RICH lesions tend to follow this classic involuting course.⁷ Non-involuting congenital hemangiomas (NICH) remain stable indefinitely and grow proportionally with the child. Partially involuting congenital hemangiomas (PICH) begin to shrink but then plateau, often leaving residual surface changes. In that same review, all PICH cases were initially diagnosed as RICH before the lesion stabilized instead of resolving completely.⁶

Kaposiform Hemangioendothelioma

Kaposiform hemangioendothelioma (KHE) is rare and falls into the locally aggressive category. It does not spread to distant organs, but it can infiltrate surrounding tissue and cause serious complications. The one that gets the most attention is Kasabach-Merritt phenomenon (KMP), a life-threatening drop in platelet count and clotting dysfunction that occurs when the tumor traps and destroys platelets.⁸ An important clarification: KMP is linked specifically to KHE and certain other rare tumors, not to common infantile hemangioma. Research established this distinction clearly in the late 1990s, yet the misconception persists.⁹ Parents told their child’s hemangioma could cause KMP are often being given outdated information. Combined therapy with sirolimus and propranolol has shown promising results in reducing tumor size in newborns with aggressive vascular tumors, with all treated patients showing marked improvement within two months in one series.¹⁰

Vascular Malformations

Malformations are the other half of the classification. They are structural defects present from birth, caused by errors in how blood or lymphatic vessels develop in the embryo. Unlike tumors, they do not involve abnormal cell growth. They are usually categorized by the type of vessel involved and whether blood flows through them quickly or slowly.

Low-Flow Malformations

Capillary malformations are the most common type of vascular malformation. The flat, pink-to-purple patches often called port-wine stains are the best-known example. They are caused by a somatic mutation in a gene called GNAQ, which occurs randomly during fetal development and is not inherited from parents.¹¹ This mutation leads to dilated, dysfunctional blood vessels in the skin.¹² When the same GNAQ mutation affects vessels in the brain or eyes, the result is Sturge-Weber syndrome, which can cause seizures and glaucoma alongside the facial birthmark. Research found this specific mutation in about nine out of ten affected tissue samples from both Sturge-Weber patients and those with port-wine stains alone.¹³

Venous malformations are soft, compressible bluish masses made of abnormally formed veins. They are the most common symptomatic vascular malformations and frequently cause pain, swelling, and functional problems. Most are caused by mutations in genes called TEK or PIK3CA. A study of over 100 patients found TEK mutations in about 43% and PIK3CA mutations in about 11%.¹⁴ These mutations disrupt normal vessel wall structure, and one of the downstream effects is abnormal activation of a clotting-related pathway that can lead to elevated D-dimer levels, a blood marker that distinguishes venous malformations from other vascular anomalies.¹⁵

Lymphatic malformations involve the lymphatic system rather than blood vessels. They appear as fluid-filled cysts or spongy masses, most often in the head, neck, or armpit. Like venous malformations, they are driven by somatic PIK3CA mutations. In one study, about half of tested children with lymphatic malformations carried a PIK3CA mutation, with the rate being higher in isolated (non-syndromic) cases.¹⁶

High-Flow Malformations

Arteriovenous malformations (AVMs) are the high-flow counterpart. In an AVM, arteries connect directly to veins without the normal capillary bed in between, creating a high-pressure shunt. This can cause pain, bleeding, skin breakdown, and, in the brain, seizures or hemorrhagic stroke. AVMs are thought to develop through a combination of genetic susceptibility and abnormal hemodynamic forces during vascular development, with epigenetic changes in endothelial cells potentially driving arteries or veins toward an abnormal state.¹⁷ AVMs are generally the most difficult vascular malformations to treat because of their dynamic blood flow and tendency to recruit new feeder vessels.

Acquired Vascular Lesions

Not all vascular lesions are present from birth. Pyogenic granulomas, for instance, are small, rapidly growing red bumps that bleed easily and often appear after minor skin injury, during pregnancy, or as a side effect of certain medications. While they are technically benign vascular tumors, they can develop at any age and arise in response to external triggers rather than congenital errors. Certain cancer drugs, particularly those targeting growth factor receptors, have been linked to drug-induced pyogenic granulomas, and combination regimens may have a synergistic effect in triggering them.¹⁸ Spider angiomas, cherry angiomas, and telangiectasias are other common acquired vascular lesions that develop in adulthood and are usually harmless.

Overlapping Syndromes

Some vascular malformations occur as part of broader syndromes that affect multiple organ systems. Sturge-Weber syndrome, mentioned earlier, is one example. Another is Klippel-Trenaunay syndrome (KTS), which involves limb overgrowth, varicose veins, and capillary malformations, typically without brain involvement. Although Sturge-Weber and Klippel-Trenaunay look clinically distinct, they share overlapping biological pathways, particularly involving the mTOR signaling pathway, and rare cases of both syndromes occurring together have been reported.¹⁹ PIK3CA-related overgrowth spectrum (PROS) is an umbrella term for conditions driven by PIK3CA mutations that can involve combinations of vascular malformations, tissue overgrowth, and skeletal anomalies. Recognizing these syndromes early matters because they require coordinated care across specialties.

How Vascular Lesions Are Diagnosed

Most vascular lesions are diagnosed clinically, meaning a doctor who sees enough of them can identify the type by examining it. When imaging is needed, Doppler ultrasound is typically the first step. It can distinguish high-flow from low-flow lesions by measuring blood velocity: arteriovenous malformations show elevated flow and arterialized veins, venous malformations show sluggish monophasic or biphasic flow, and lymphatic malformations often show no internal flow at all.²⁰

MRI is the gold standard for defining the full extent of a malformation, especially before planning treatment. It reveals how deep the lesion goes, whether it involves muscle or bone, and how the venous drainage is configured. Dynamic MRI sequences are particularly useful for separating high-flow from low-flow lesions by measuring how quickly contrast agent arrives.²¹ Some vascular lesions can also be detected prenatally on routine ultrasound, and fetal MRI can further characterize them, which helps plan delivery and early postnatal care.²²

Treatment Approaches

Treatment depends entirely on what kind of vascular lesion you are dealing with, its size, its location, and how much trouble it is causing. Many lesions, especially small capillary malformations or involuting hemangiomas, need no intervention beyond monitoring.

Sclerotherapy

For venous malformations that cause pain or functional problems, sclerotherapy is often the go-to procedure. A sclerosing agent is injected directly into the malformation to damage the abnormal vessel lining, triggering clotting and eventually shrinking the lesion. Ethanol has long been used as a powerful sclerosant, but a foam combination of bleomycin and polidocanol (BPF) has emerged as a gentler alternative. In a comparative study, BPF achieved similar effectiveness to absolute ethanol but with a better safety profile and fewer treatment sessions needed.²³ The foam structure displaces blood and increases contact time between the agent and the vessel wall, which is part of why it works efficiently.

Laser Treatment

Pulsed dye laser (PDL) remains the primary treatment for port-wine stains and other superficial capillary malformations. The laser targets the red pigment in blood, heating and collapsing the dilated vessels beneath the skin. Results vary considerably from patient to patient. Emerging research using a specialized skin imaging technique has found that vessel diameter may predict who responds well: patients whose malformed vessels are wider than about 40 micrometers tend to have significantly better laser outcomes, while those with smaller vessels show poorer responses.²⁴ This may explain the frustration many patients feel after multiple laser sessions with limited improvement and could eventually help doctors set more realistic expectations before starting treatment.

Surgery

Surgical removal is considered when a lesion is well-defined, accessible, and causing symptoms that other treatments cannot address. For venous malformations of the hand in children, for instance, surgery is pursued when there is pain and loss of function and when the lesion appears completely resectable on imaging.²⁵ The risk with surgery is always that incomplete removal can lead to regrowth, especially with malformations that infiltrate surrounding tissue. For AVMs, surgery is sometimes combined with pre-operative embolization to reduce blood flow first.

Targeted Molecular Therapies

The discovery that many vascular malformations are driven by specific gene mutations has opened the door to precision medicine. Sirolimus, which inhibits the mTOR pathway, was one of the first drugs repurposed for this. More recently, alpelisib, a drug originally developed for breast cancer, has shown striking results because it targets the PI3K-alpha protein, the exact enzyme that PIK3CA mutations make overactive.

In a study of patients with severe vascular malformations carrying PIK3CA or TEK mutations, alpelisib treatment led to radiological improvement in most cases. Patients with PIK3CA mutations responded especially well, with an average volume reduction of about 53%, compared with about 21% in those with TEK mutations. Elevated D-dimer levels, a chronic problem for many patients with venous malformations, also improved steadily during treatment. Side effects were generally manageable, though one patient developed significant blood sugar elevation requiring insulin.²⁶ A larger observational study found that about 92% of patients treated with alpelisib for more than three months showed improvement in their vascular anomaly-related symptoms, including many whose malformations did not fit neatly into the PIK3CA-related overgrowth spectrum that the drug was originally studied for.²⁷

The practical question for patients and families is whether genetic testing of the lesion is worth pursuing. For mild or easily managed malformations, it rarely changes the treatment plan. But for large, painful, or functionally impairing malformations that have not responded to conventional approaches, identifying the specific mutation can now open the door to drugs like alpelisib or guide enrollment in clinical trials. A separate trial of alpelisib specifically in patients with PIK3CA-related overgrowth spectrum found that roughly a third of patients achieved a 20% or greater reduction in target lesion volume within six months.²⁸

Living with a Vascular Lesion

The physical symptoms of vascular malformations, including pain, swelling, and bleeding, get most of the clinical attention. But the psychological burden is substantial and often underestimated. A study from a specialist center in the United Kingdom found that patients with vascular malformations scored significantly worse than the general population across all quality-of-life domains, with women reporting lower physical and social functioning and more depression than men.²⁹

Research in Asian patients found that about 42% of adults with vascular malformations had measurable psychosocial illness, and nearly all patients showed some degree of difficulty participating in normal social roles and activities.³⁰ Venous and lymphatic malformations tended to carry the heaviest psychosocial burden, likely because of their chronic pain and visible swelling, whereas port-wine stains scored somewhat lower, perhaps because they are flat and painless even if cosmetically distressing.

For children and teenagers with visible vascular lesions, cosmetic camouflage can make a meaningful difference. One study measured quality of life in young patients before and after being introduced to medical-grade concealing makeup, and found that the negative impact of visible vascular anomalies was largely eliminated by camouflage use.³¹ This is a low-cost, low-risk intervention that is rarely discussed in clinical settings but can substantially improve a child’s daily experience while waiting for other treatments to take effect or when treatment is not warranted.