For the parents of babies, a correct understanding of the classification of hemangioma is conducive to early and correct treatment and eventually achieving a perfect result of scarless cure. There is no unified standard for the clinical classification of hemangioma, but there are mainly two classification methods as follows: 1. Morphological classification The classification method based on histological structure and clinical signs. Hemangioma is classified into capillary hemangioma (nevus and strawberry hemangioma), cavernous hemangioma, trabecular hemangioma and mixed hemangioma, etc. This classification method is still used in most textbooks. 2.Cytological classification In 1982, Mulliken divided traditional hemangiomas into two categories: hemangiomas and vascular malformations by culturing specimens of vascular endothelial cells in hemangiomas and finding that they have the dual characteristics of tumors and malformations. Hemangioma: It is characterized by the proliferation of vascular endothelial cells and the formation of a large number of new capillaries, with clinical manifestations of strawberry hemangioma, cavernous capillary hemangioma and mixed hemangioma. Vascular malformation: It is a developmental malformation of the vascular system, mainly blood vessels, while the endothelial cells of blood vessels are normal. They are further classified according to anatomical and hematologic features: ① Low-flow vascular malformations include capillary malformations, venous malformations and lymphatic vascular malformations; ② High-flow vascular malformations include arteriovenous malformations, arteriovenous malformations and arteriovenous fistulas. ③Hemangioma vascular malformations include capillary hemangioma (nevus and strawberry hemangioma), cavernous hemangioma, trabecular hemangioma and mixed hemangioma. Pathogenesis of hemangioma The mechanism of hemangioma and vascular malformation is not fully understood, but most studies suggest that they are diseases related to blood vessel formation. Angiomas (endothelial cell proliferation) may be caused by increased levels of pro-angiogenic factors and decreased levels of growth inhibitory factors; vascular malformations are structural abnormalities caused by genetic mutations during embryonic angiogenesis and angiogenesis. Levels of estrogen and estrogen receptors are significantly higher in angiodysplasia than in vascular malformations. Vascular endothelial growth factor (VEGF) is increased in hemangiomas and normal in vascular malformations. Clinical manifestations of hemangioma (a) Hemangioma Hemangioma is the most common benign tumor in infants and young children (incidence of infants and young children is 1%-2%, and the ratio of male to female is about 1/3), and is almost always found from birth to shortly after birth, according to statistics 75% of cases occur at birth, the remaining 25% are found in infancy or childhood, and a few are found in adulthood. Hemangiomas are most frequent on the head and face, with the rest on the extremities, trunk, and internal organs. Depending on the depth of distribution of the lesion, there are different signs and symptoms, and the more superficial ones (located in the papillary layer of the dermis) are often called “strawberry hemangioma”; those involving the deeper dermis, subcutaneous or intramuscular layers are often called “spongy capillary hemangioma”; when both exist together, they are called “mixed hemangioma”. When both of them exist, it is called “mixed hemangioma”. (B) Vascular malformations Vascular malformations are present at birth, and capillary malformations are often obvious at birth, while arterial and arteriovenous malformations are often not obvious in infancy (trabecular hemangioma). Vascular malformations do not have the characteristic of naturally fading during the growth of children, and can gradually worsen. 1.Capillary malformation (nevus): it is patchy, and the damage can be hypertrophic with age, and the surface is nodular and warty. 2, venous malformation: belongs to low-flow vascular malformation, manifested as a lump under the skin or mucous membrane or a purple-blue surface, mild vascular filling, varicose veins, easily compressed, changing with the change of body position (such as low hanging, crying or struggling to increase), soft texture, there are often venous stones in the lump, and emboli can be touched. 3. Arteriovenous malformation: It belongs to high blood flow vascular malformation, including arteriovenous malformation, arteriovenous malformation and arteriovenous fistula. The typical arteriovenous malformation is characterized by thick, pulsating vessels in the form of rosettes or cords in the lesion and surrounding area, with surface temperature higher than normal skin, and continuous tremor can be detected and a continuous blowing murmur can be heard locally. Arteriovenous malformations can cause “blood theft”, resulting in ischemic necrosis, ulceration, pain, and increased cardiac output of the affected skin. (C) Differential diagnosis of hemangioma and vascular malformation: hemangioma and vascular malformation are two different vascular diseases, their treatment and prognosis are different, so in the diagnosis of hemangioma, attention should be paid to differentiate from vascular malformation. In general, hemangioma and vascular malformation can be differentiated by the following aspects: ① Time of onset: hemangioma mostly appears 1 week to 1 month after birth, while vascular malformation mostly appears at birth; ② Growth rate: hemangioma mostly has a rapid growth (growth phase) and slow receding (receding phase) process. The color of superficial hemangioma is bright red, and gradually deepens during the proliferation phase, then changes from bright red to dark purple when it starts to recede, and finally becomes florid. The skin on the surface of deep hemangiomas is elevated, normal in color or translucent blue. Vascular malformations have different colors depending on the capillary lymphatics, veins or arteries they contain; ④ Temperature of the lesion area: normal or slightly elevated for hemangiomas, significantly elevated or normal for vascular malformations; ⑤ Texture: hemangiomas are rubber-like and cannot be emptied of the blood in them by pressure, negative postural tests, and receding hemangiomas are residual fibrofatty tissue with a softened texture; whereas vascular malformations are soft, easily compressed and (6) Imaging examination: mainly color ultrasound and MRI. color ultrasound can distinguish between hemangioma and vascular malformation, and further distinguish various types of vascular malformation. Color ultrasound can show the level, size and blood supply of lesions, which is very helpful for treatment; MRI: it can show both the scope of lesions and the characteristics of blood rheology, which is the gold standard for distinguishing hemangioma and vascular malformation examination; 3D CT: it is helpful for differential diagnosis because it can clearly show the condition of blood vessels in lesions and their anatomical relationship with surrounding tissues.