Vascular tumors are growths that arise from the cells lining blood vessels or lymphatic vessels, driven by abnormal cell proliferation. They range from harmless birthmarks that disappear on their own to aggressive cancers, and they are formally distinguished from vascular malformations, which are structural defects in vessels that a person is born with but that do not involve true cell overgrowth.1PubMed Central. ISSVA Classification of Vascular Anomalies and Molecular Biology Understanding where a particular vascular tumor falls on the spectrum from benign to malignant shapes everything about how it is monitored, treated, and what a patient can expect long term.
Why Classification Matters So Much
For decades, doctors used the word “hemangioma” loosely to describe almost any vascular growth, which led to confusion and sometimes wrong treatments. A baby’s common birthmark and a rare cancerous blood-vessel tumor might both have been called hemangiomas despite having nothing in common biologically. The International Society for the Study of Vascular Anomalies (ISSVA) developed a classification system to fix this. It draws a hard line between vascular tumors, which involve proliferating endothelial cells, and vascular malformations, which are structural channel defects present from birth that grow proportionally with the child but do not involve true cell multiplication.1PubMed Central. ISSVA Classification of Vascular Anomalies and Molecular Biology
The most recent update to the ISSVA classification keeps the core framework of dividing vascular tumors into benign, borderline (sometimes called locally aggressive or intermediate), and malignant categories. It also added a new grouping called Potentially Unique Vascular Anomalies for lesions that do not yet fit neatly into existing categories.2PubMed Central. Updated Classification of Vascular Anomalies Getting the classification right is not just academic bookkeeping. The disease course and treatment options differ enormously depending on which vascular anomaly a patient actually has, and mislabeling can lead to delayed or inappropriate care.
Benign Vascular Tumors
The single most common vascular tumor is the infantile hemangioma. It appears in the first weeks of life, grows rapidly for about six to eight months, and then slowly shrinks on its own over the next several years.3PubMed Central. Glucose transporter 1-positive endothelial cells in infantile hemangioma exhibit features of facultative stem cells Most infantile hemangiomas are small, superficial, and need no treatment at all. They are far more common in girls than in boys, and premature infants face higher risk. The hallmark laboratory feature is that the endothelial cells lining these tumors express a glucose transporter protein called GLUT1, which is reliably positive in about 95% of infantile hemangiomas but absent in vascular malformations. This makes GLUT1 staining a useful diagnostic tool when the clinical picture is unclear.4PubMed. The utility of GLUT1 as a diagnostic marker in cutaneous vascular anomalies: A review of literature and recommendations for daily practice
Congenital hemangiomas are a separate entity. Unlike infantile hemangiomas, they are fully formed at birth. They come in distinct subtypes: rapidly involuting congenital hemangiomas (RICH), which shrink quickly in the first year of life; noninvoluting congenital hemangiomas (NICH), which persist; and partially involuting congenital hemangiomas (PICH), which fall somewhere in between.5PubMed. The histopathology of congenital haemangioma and its clinical correlations: a long-term follow-up study of 55 cases Congenital hemangiomas are GLUT1-negative, which helps distinguish them from infantile hemangiomas when both present in infancy.6PubMed. Congenital hemangiomas and infantile hemangioma: missing links The rapidly involuting type can sometimes cause a brief but notable drop in platelet counts in the first few days of life, so newborns with large RICH lesions are monitored closely.
Pyogenic granulomas are another common benign vascular tumor that many people have seen without knowing what they were. They are small, bright red, and tend to bleed easily. Despite the name, they are neither infected (pyogenic) nor true granulomas. They pop up after minor skin trauma, during pregnancy, or sometimes for no clear reason. Most are treated with simple excision or cauterization.
Borderline Vascular Tumors
The borderline, or locally aggressive, category captures tumors that do not typically spread to distant organs but can cause serious problems through local growth and complications. The most clinically significant is kaposiform hemangioendothelioma (KHE), a rare tumor that usually appears in infancy or early childhood. KHE is often associated with a dangerous clotting disorder called Kasabach-Merritt phenomenon, in which the tumor traps platelets and clotting factors, causing severe thrombocytopenia and sometimes life-threatening bleeding.7PubMed Central. Kaposiform Hemangioendothelioma with Kasabach-Merritt Phenomenon in a Neonate – Role of Dual Therapy: A Case Report and Review of Literature In newborns, KHE with severe Kasabach-Merritt phenomenon carries a high mortality rate, making early recognition and treatment critical.8PubMed. Kaposiform hemangioendothelioma with Kasabach-Merritt phenomenon: successful treatment with embolization and vincristine in two newborns
Epithelioid hemangioendothelioma (EHE) sits in a grey zone. It is technically classified as a vascular sarcoma and behaves unpredictably. Some cases act like low-grade tumors that remain stable for years, while others behave like aggressive cancers with widespread organ involvement.9PubMed Central. Epithelioid hemangioendothelioma, an ultra-rare cancer: a consensus paper from the community of experts EHE typically presents around age 50, though it can occur at any age, and it has a tendency to involve the liver, lungs, bone, and soft tissue. A defining feature is the presence of specific fusion genes, most commonly WWTR1-CAMTA1 or YAP1-TFE3, which aid in diagnosis.10Japanese Journal of Clinical Oncology. Epithelioid hemangioendothelioma—its history, clinical features, molecular biology and current therapy In cases of EHE confined to the liver, transplantation has shown promising outcomes, with five-year survival rates reaching about 81% in European registry data.11PubMed Central. Malignant hepatic vascular tumors in adults: Characteristics, diagnostic difficulties and current management
Malignant Vascular Tumors
Angiosarcoma is the most feared vascular tumor. It is a frankly malignant cancer of endothelial cells that can arise anywhere in the body, though it most commonly appears on the skin of the head and neck.12Gynecologic Oncology Reports. Radiation-induced angiosarcoma of the vagina and vulva: Case report and review of literature Two well-established risk factors stand out: chronic lymphedema and prior radiation therapy. When radiation-induced angiosarcoma develops, it typically appears years after the original treatment, presumably because radiation damages DNA in the vessel-lining cells over time.13PubMed Central. When Radiation Therapy Becomes a Foe: A Rare Case of Radiation-Induced Angiosarcoma of Head and Neck Angiosarcoma carries a poor prognosis overall. High-grade angiosarcomas often show amplification of the MYC gene, which contributes to their aggressive behavior.14PubMed Central. The genetics of vascular tumours: an update For liver angiosarcoma specifically, outcomes after transplantation have been so poor, with survival averaging only about six to seven months due to rapid recurrence, that the disease is generally considered a contraindication to liver transplant.11PubMed Central. Malignant hepatic vascular tumors in adults: Characteristics, diagnostic difficulties and current management
Kaposi sarcoma is the other major malignant vascular tumor. It is caused by human herpesvirus 8 (HHV-8), also called Kaposi sarcoma-associated herpesvirus, which was identified in 1994. The virus is strongly linked to all subtypes of Kaposi sarcoma, including the classic form seen in older men, the endemic form in sub-Saharan Africa, the transplant-associated form, and the epidemic form seen in people with AIDS.15PubMed Central. Spectrum of Kaposi’s sarcoma-associated herpesvirus, or human herpesvirus 8, diseases With effective HIV treatment, the AIDS-associated form has become less common in places with good access to antiretroviral therapy, though it remains a major concern in areas where treatment access is limited.
Common Symptoms and Warning Signs
The symptoms of vascular tumors vary enormously based on the type, location, and size. Benign infantile hemangiomas usually appear as raised, red or purplish patches on the skin during the first weeks of life, growing rapidly for several months before beginning to flatten and fade. Deep hemangiomas may have a bluish tint and sit beneath the surface, sometimes being mistaken for a bruise. Most are painless, but hemangiomas near the eye, airway, or in the liver can cause functional problems and need prompt evaluation.
Borderline tumors like KHE often present as a firm, reddish-purple mass that feels warm to the touch. The Kasabach-Merritt phenomenon that frequently accompanies KHE produces easy bruising, petechiae (tiny pinpoint red spots on the skin), and sometimes life-threatening bleeding. These clotting-related signs in a baby with a vascular mass are a medical emergency.
Malignant vascular tumors are more insidious. Angiosarcoma can look deceptively innocent at first, sometimes resembling a bruise or a small wound that will not heal. On the scalp or face, it might present as a painless violet patch that slowly expands. Internal angiosarcomas in the liver or spleen may not cause symptoms until they are advanced, sometimes presenting with unexplained weight loss, abdominal pain, or sudden internal bleeding. Kaposi sarcoma typically shows up as painless purple, red, or brown blotches on the skin or inside the mouth, sometimes with swelling in the legs. Any vascular-looking skin lesion that is growing, changing color, bleeding easily, or not healing deserves medical attention.
How Vascular Tumors Are Diagnosed
Many benign vascular tumors can be diagnosed clinically, especially infantile hemangiomas in infants with a classic presentation. Ultrasound with Doppler is usually the first imaging step, as it shows blood-flow patterns and can help distinguish a vascular tumor from a malformation or a non-vascular mass. MRI is the gold-standard imaging tool for deeper or more complicated lesions, giving detailed views of how far the tumor extends into surrounding tissue.
When imaging alone is not enough, biopsy provides a definitive answer. Pathologists use immunohistochemical stains to identify the origin of the cells. Markers like CD31 are particularly helpful because they have strong specificity for endothelial cells, while stains like GLUT1 can confirm an infantile hemangioma diagnosis as discussed earlier.16PubMed. GLUT1: a newly discovered immunohistochemical marker for juvenile hemangiomas A lymphatic endothelial marker called LYVE-1 can also be informative: it tends to be negative in most benign blood-vessel tumors but positive in angiosarcomas and Kaposi sarcomas, which may reflect the ability of malignant vascular cells to co-opt lymphatic characteristics.17PubMed. Expression of a lymphatic endothelial cell marker in benign and malignant vascular tumors
Misdiagnosis remains a real problem in this field. Certain soft-tissue sarcomas can mimic vascular anomalies on physical exam and even on imaging, leading to delays in diagnosis and suboptimal outcomes.18Oncology Reviews. Diagnostic pitfalls: soft-tissue sarcomas initially misdiagnosed as benign vascular anomalies—a case report and systematic review This is one reason that any vascular lesion that behaves unexpectedly, grows at an unusual rate, or does not fit the expected pattern for a benign tumor should prompt biopsy rather than watchful waiting.
Treatment Approaches
Treatment depends entirely on where a vascular tumor sits on the benign-to-malignant spectrum and whether it is causing problems.
Benign Tumors
Most small infantile hemangiomas need nothing more than monitoring, since they shrink on their own. For hemangiomas that are large, ulcerated, located near the eye or airway, or causing functional problems, propranolol has become the first-line treatment. This beta-blocker, originally a heart medication, was discovered to shrink hemangiomas almost by accident. It works through multiple mechanisms, including constricting the small blood vessels feeding the tumor and suppressing the growth signals that endothelial cells rely on.19PubMed Central. Mechanisms of propranolol action in infantile hemangioma The response can be dramatic, not merely stabilizing the hemangioma but driving it toward complete resolution faster than nature would.20British Journal of Dermatology. The use of propranolol in the treatment of infantile haemangiomas: an update on potential mechanisms of action Before propranolol entered the picture in 2008, the mainstay was oral corticosteroids, which worked but came with far more side effects. Propranolol transformed the management of problematic infantile hemangiomas in a way few drugs have in pediatric medicine.
Borderline and Complex Tumors
For tumors like KHE with Kasabach-Merritt phenomenon, treatment is more aggressive. Vincristine, a chemotherapy drug, has historically been used, sometimes combined with embolization to cut off blood supply to the tumor.8PubMed. Kaposiform hemangioendothelioma with Kasabach-Merritt phenomenon: successful treatment with embolization and vincristine in two newborns More recently, sirolimus (also known as rapamycin) has emerged as an effective option for complicated vascular anomalies that cannot be surgically removed. In one prospective study of 57 patients with various complicated vascular anomalies treated with sirolimus, the majority showed a partial response, with the drug generally well tolerated.21PubMed Central. Efficacy and Safety of Sirolimus in the Treatment of Complicated Vascular Anomalies Sirolimus works by blocking a growth-promoting signaling pathway that is overactive in many vascular tumors and malformations.
Malignant Tumors
Angiosarcoma treatment typically involves surgery, radiation, and chemotherapy, often in combination. These tumors are notoriously difficult to cure because they tend to infiltrate widely beyond their visible margins. Preoperative embolization, where doctors thread a catheter into the blood vessels feeding the tumor and block them with particles or coils, can reduce blood loss during surgery and improve outcomes.22PubMed Central. Preoperative embolization of brain, head, and neck tumors: Single center experience and literature review For Kaposi sarcoma, treating the underlying HHV-8 infection and, in AIDS patients, starting or optimizing antiretroviral therapy can lead to substantial regression of the tumors. Chemotherapy is added for more advanced or visceral disease.
The Genetic Landscape and Targeted Therapies
The last two decades of research have dramatically reshaped our understanding of what causes vascular tumors at the molecular level. Inherited and somatic mutations in several key growth-signaling pathways have been identified, and many of these pathways already have drugs developed against them for other cancers.23PubMed. Genetic Basis and Therapies for Vascular Anomalies This has opened the door to repurposing existing targeted therapies for vascular tumors.
One promising avenue involves MEK inhibitors, a class of drugs already approved for certain melanomas and other cancers. In a mouse model of vascular tumors driven by a mutation in the GNAQ gene, the MEK inhibitor trametinib reduced abnormal blood vessel growth, reversed platelet depletion, and extended the animals’ survival. Treated mice showed vascular density returning to levels comparable to healthy controls and significantly lower levels of D-dimer, a marker of clotting problems.24PubMed Central. MEK inhibition reduced vascular tumor growth and coagulopathy in a mouse model with hyperactive GNAQ While these are animal results, they represent the kind of mechanism-targeted approach that is moving into clinical trials for patients with vascular tumors that do not respond to existing treatments.
Beyond fusions and point mutations, high-grade angiosarcomas frequently show amplification of the MYC gene, and various hemangiomas harbor somatic mutations in genes like GNA and IDH.14PubMed Central. The genetics of vascular tumours: an update Each of these findings represents a potential therapeutic target. The field is moving toward a model where the specific genetic alteration driving a patient’s tumor guides the choice of drug, rather than treating all vascular tumors with the same chemotherapy regimen.
The Value of Multidisciplinary Care
Vascular tumors can involve the skin, bones, internal organs, and the clotting system all at once, which means no single specialist has the full picture. This is why the field has moved heavily toward multidisciplinary vascular anomalies teams, typically including dermatologists, interventional radiologists, surgeons, hematologists, and sometimes cardiologists or geneticists, depending on the case.25PubMed. How we established a multidisciplinary program for vascular anomalies A decade-long review of one such pediatric program found that a collaborative committee contributed to improved diagnostic accuracy and better clinical outcomes, largely because specialists catch things that would be missed in a solo-practice setting.26PubMed. Role of a Multidisciplinary Vascular Anomalies Committee in the Management of Pediatric Patients: A Decade-Long Experience
If you or your child has a vascular anomaly that is complicated or unclear, seeking out a center with a dedicated vascular anomalies team is one of the most practical things you can do. These programs are becoming more common at academic medical centers, and they can often evaluate patients remotely to determine whether a referral is warranted.
Psychological and Social Effects in Children
Something often overlooked in discussions of vascular tumors is their psychological impact, particularly when they appear on the face. A study examining preteen children with facial infantile hemangiomas found that while overall social anxiety levels were not higher than average, children who had not received treatment showed significantly greater anxiety in new social situations and scored lower on social initiative compared to those who had been treated.27JAMA Otolaryngology–Head & Neck Surgery. Social Impact of Facial Infantile Hemangiomas in Preteen Children This finding adds weight to the argument for treating visible hemangiomas early when possible, even if the tumor itself would eventually regress. By the time a facial hemangioma fully involutes on its own, the child may have spent several formative years navigating staring, questions, and self-consciousness.
Residual changes also matter. Even after an infantile hemangioma regresses, the affected skin may have a different texture, be slightly discolored, or have excess fibrofatty tissue. Cosmetic procedures like laser treatment or surgical revision can address these remnants, but families are not always told about these options. If a hemangioma has left behind a visible mark, it is reasonable to ask about referral to a dermatologist or plastic surgeon who works with vascular lesion remnants.