Hemangioma, also known as infantile hemangioma, is the most common benign tumor in infants and children. It is a true vascular tumor, caused by the overproliferation of normal vascular tissue in the mesoderm. Hemangiomas are usually found on the head, face and neck, followed by the extremities and trunk. The incidence is 1.1%-2.6% in newborns and about 30% can be seen at birth, usually growing slowly at 2 or 4 weeks after birth, thus the incidence is 10%-12% at the age of 1 year. Female infants are more common than male infants, with a ratio of 2 to 5:1, and multiple cases account for 15% to 30%. Most hemangiomas occur in the skin or subcutaneous tissues and are divided into proliferative, regressive, and complete stages according to the process of lesion development. This typical feature is an important basis for its differentiation from vascular malformations. Although most hemangiomas regress on their own, the proliferation and regression rates are not the same. Proliferative hemangiomas often initially appear as pale spots, followed by capillary dilation surrounded by a halo-like whitish area. Infants and children exhibit two typical periods of rapid growth within the first year of life, with the first period of rapid growth occurring 4 to 6 weeks after birth and the second at 4 to 5 months. Hemangiomas grow rapidly during these 2 periods and exhibit corresponding clinical symptoms such as tenderness, ulceration, and bleeding. The clinical manifestations of hemangiomas depend on the location and size of the lesion and the period in which the lesion occurs. More superficial proliferative hemangiomas often appear as bright red spots or nodular lesions, while more advanced lesions have a cyanotic surface or no color change. The regressive phase usually occurs by the end of the first year of life (12 to 18 months), when the growth rate of the tumor slows. The transition from the proliferative phase to the regressive phase is a gradual process, with the regressive phase being preceded by a significant slowing of growth and softening of the texture of the tumor. When a cutaneous or subcutaneous hemangioma enters the regressive phase, the color of the tumor changes from bright red to dark gray, and the tumor gradually fades and shrinks. It is generally believed that the natural regression rate is 50% to 60% within 5 years of age, 75% within 7 years of age, and up to 90% or more within 9 years of age. Most cases undergo a regression period of 2 to 5 years. However, 24% of patients have distant secondary malformations, and 38% of patients require second-stage reconstruction of the regressed hemangioma lesion. Unless the hemangioma is extremely inconspicuous, it needs to be treated appropriately and early. Hemangiomas are classified into 3 types depending on the depth of the site of occurrence 1. superficial hemangioma Refers to hemangiomas located in the papillary dermis 2. deep hemangioma Refers to hemangiomas located in the reticular dermis or subcutaneous tissue 3. compound hemangioma Refers to both and needs to be distinguished from venous malformations with care. This reasonable and simplified classification method is generally accepted because it is easy to use in clinical observation. According to the distribution characteristics, hemangiomas can be divided into 2 types: focal and segmental. Solitary focal hemangiomas have a typical proliferative and regressive phase, while multiple focal hemangiomas may have multiple, small, scattered lesions involving the skin, liver, and gastrointestinal tract. If the number of hemangiomas is more than 5, combined gastrointestinal and hepatic hemangiomas are highly likely and an abdominal ultrasound should be performed. Segmental hemangiomas are usually multiple, involving multiple subunits of the adjacent face, with indistinct demarcation, and are mostly distributed along the trigeminal nerve area, especially in areas with beards. Congenital hemangioma is a special type of infantile hemangioma, also known as congenital non-progressive hemangioma, which is characterized by being present at birth and completing growth; a few are detected during fetal ultrasonography. Congenital hemangiomas include 2 subtypes, namely, nonresolving congenital hemangiomas and rapidly regressing congenital hemangiomas. Multiple hemangiomas involving the face, neck, and chest are called PHACES syndrome and present as: 1) posterior cranial fossa malformation; 2) facial and cervical hemangioma; 3) arteriovenous malformation; 4) cardiac malformation; 5) ocular malformation; and 6) sternal or abdominal cleft or cardiac ectasia. The diagnosis is confirmed by the presence of several of these. Its clinical manifestations are complex, with more than 50 corresponding systemic lesions reported, such as cerebellar or carotid artery hypoplasia, ductus arteriosus, optic nerve atrophy, and small jaw malformation. Among them, the distribution of facial hemangiomas is characteristic, often in patches or plaques in specific areas, such as the frontotemporal, maxillary, temporomandibular and frontonasal regions (segmental hemangioma), suggesting that they may be caused by developmental defects in certain regions. It has been found that about 62% of patients with lesions that can regress before the age of 6 years achieve optimal aesthetic results after the tumor regresses; however, about 80% of patients with lesions that cannot regress before the age of 6 years develop facial scarring, excess skin, and capillary dilation after the hemangioma regresses. The microscopic manifestation of hemangioma in regression is the appearance of a large number of mast cells within the hemangioma, the gradual loss of proliferative capacity of vascular endothelial cells, their flattening, and the reduction of blood vessels, and the transformation of the lesion from a solid tumor dominated by proliferating active vascular endothelial cells to a lesion dominated by fibrofatty tissue and luminal structures. Recent studies have found strong positive immunoreactivity for placenta-related vascular antigens FcyRII, LeY, merosin, and GLUT1 in hemangiomas, and negative in vascular malformations. The major damage in infantile hemangiomas often comes not from the lesion itself but from overtreatment. Past cases treated with surgery, freezing, laser, radiation, and sclerotherapy have been followed up longitudinally and confirmed to have unsatisfactory sequelae damage and cosmetic results. Complications of aggressive treatment can reach 50% and have a 30% recurrence rate. Therefore, it should be emphasized that the aim of treatment is not only to eliminate the lesion, but also to maintain healthy normal tissue and appearance. Tumor volume should be carefully measured and photographed in hemangioma cases, detailed records should be made, and regular follow-up observations should be conducted. At the same time, the pros and cons of active treatment should be patiently explained to parents to eliminate their concerns and urgency to seek treatment, and frequent guidance should be given. The only time to receive medication, pressure bandage, laser and surgery is when: 1. rapid growth of hemangioma; 2. large hemangioma with bleeding, infection or ulceration; 3. affecting the patient’s vital functions, such as feeding, breathing, swallowing, hearing, vision, excretion or motor functions; 4. with thrombocytopenia syndrome; 5. combined with high output congestive heart failure; 6. structures, such as eyelids, nose, lips, auricles, etc. However, no treatment can be as satisfactory as complete regression on its own. According to the guidelines for infantile hemangiomas proposed by the American Academy of Dermatology in 1997, exactly how to treat hemangiomas clinically should depend mainly on the site, depth (superficial, deep, mixed), extent and size of the lesion, staging (proliferative phase, regressive phase), the presence of functional impairment, the treatment experience of the treating physician, the effectiveness of specific treatment methods, and the expectations of the child’s family. At present, the main methods of treatment for hemangioma are waiting observation, drug treatment, laser treatment and surgery. Hemangioma should be treated in a gradual and progressive manner. Hemangiomas in the stable or receding stage can be closely observed; in other cases, oral propranolol treatment (first-line treatment) is preferred. Huge hemangiomas that involve important areas (e.g., nose, eyelids) or affect function (e.g., breathing, vision) may also be treated surgically at an early stage. The aim of surgical treatment is to improve aesthetics and function, and the pursuit of surgical completeness is not advocated. It is generally limited to the treatment of fibrofatty tissue remnants by various techniques, i.e., removal of excess fibrofatty tissue and correction of cosmetic deformities. Even for large hemangiomas, the surgeon should evaluate the indications for early surgery after always considering the use of less invasive treatments such as drugs and/or lasers to rapidly improve the condition, weighing the pros and cons. For hemangiomas that can only be partially removed surgically, surgery can be combined with other treatments such as medication and laser therapy. Indications for surgery: 1) hemangiomas with residual fibrofatty tissue that are expected to fade and grow rapidly; 2) nodular giant hemangiomas involving anatomical areas where scars are easily concealed, such as the neck and scalp; 3) myxoid hemangiomas with narrow tumor bases; 4) congenital hemangiomas that do not fade; 5) eyelid hemangiomas with secondary eyelid dyskinesia that do not respond to drug and/or laser therapy; 6) hemangiomas causing nasal Hemangioma with ulceration and bleeding that is not effective for corticosteroid and/or laser treatment. Parents of children with hemangioma always have high hopes for laser treatment. Although many units are carrying out clinical work on laser treatment of hemangioma, the value of laser treatment for infantile hemangioma is actually very limited. This is because laser is a physical therapy, and for hemangiomas in the proliferation phase, laser treatment alone cannot control the continued growth of hemangiomas. Secondly, the penetration depth of laser is limited (average penetration depth is 1.2mm) and is not effective for deep (subcutaneous) hemangiomas. If the power is increased, regrettable scarring and pigmentation changes are often left behind. Therefore, laser treatment of hemangiomas is limited to superficial skin hemangiomas that have stopped growing and are less than 2 mm thick. Parents should be encouraged to use laser treatment as the definitive treatment for residual capillary dilation rather than as a routine for hemangiomas, especially for lesions on the nose and lips. Atrophic scarring that remains after regression or treatment of hemangioma can be treated with fractional laser. Capillary dilation that remains after regression or treatment can be treated by local injection of 0.25% polyglaucine or 0.2% sodium tetradecyl sulfate, or by laser treatment. Residual lesions or skin erythema after treatment can be treated with a pulsed fuel laser. Repeat laser treatment is available for 4 to 6 weeks. For children with hemangioma with thrombocytopenia syndrome, a combination of oral propranolol and corticosteroids (prednisone) is preferred, and vincristine may also be used for treatment.