Hemangioma is most often seen in infants at birth (about 1/3) or shortly after birth (within 1 month). It originates from residual embryonic angiogenic cells. Eighty percent of these tumors are congenital. The incidence is about 10%, more common in females, with a ratio of 3:1-5:1, and 22% in preterm infants with a birth weight of less than 1,000 g. Hemangiomas are benign and grow slowly. Hemangiomas are benign, slow-growing and rarely malignant. It is one of the most common benign tumors in children. The growth can be divided into three stages: proliferative stage, quiescent stage (or pre-abscession) and abcession (post-abscession) stage. It has the biological characteristics of proliferation of vascular endothelial cells and natural regression after proliferation, and often appears in the neonatal period, and enters into the proliferative stage after 2-3 months, the tumor body increases rapidly, and stops growing and degenerates gradually from 6 months to about 1 year old, and the latest age of regression is reported in the literature to be before the age of 10 years old. The rate of regression can be as high as about 80%. Pathogenesis The etiology, pathology, growth mechanism and biological characteristics of the tumor are not fully understood. Currently, most scholars believe that during the development of human embryos, especially in the early stage of vascular tissue differentiation, due to the small-scale misconfiguration of its controlling gene segments, it leads to abnormal tissue differentiation in specific areas and develops into hemangioma. Some scholars also believe that in the early embryonic stage (8-12 months), the embryonic tissue suffers mechanical injury and local tissue hemorrhage, resulting in the distribution of some hematopoietic stem cells to other embryonic characteristic cells, and some of them differentiate into vascular-like tissues and eventually form hemangiomas. The histopathological characteristics of hemangiomas are that the tumors are rich in hyperplastic vascular endothelial cells, with angiogenesis and mast cell aggregation. Clinical manifestations Hemangiomas occurring in the oral and maxillofacial region account for about 60% of all hemangiomas in the body, most of which occur in the skin and subcutaneous tissue of the face and neck, and very few of them are found in the oral mucosa. Most of the deep or visceral hemangiomas grow in the subcutaneous tissue, but also in the muscle, and a few can be in the bone or viscera and other parts of the body. Subcutaneous hemangiomas may be slightly elevated, with normal or cyanotic skin and soft, well-defined masses. Approximately 80% of hemangiomas are solitary lesions and 20% are multiple. The biological behavior of hemangiomas is such that they can spontaneously regress. The course of the disease can be divided into 3 phases: proliferative phase, regressive phase and regressive completion phase. The proliferative stage is initially characterized by capillary dilatation, surrounded by a halo-like white area; it quickly becomes erythematous and rises above the skin, unevenly resembling the shape of poplar (grass) plums. With the first growth and development period of infants, it grows rapidly after about 4 weeks, which is often the most urgent period for parents to seek treatment. If it grows on the face, it can not only cause deformity, but also affect the motor function, such as closing the eyes and opening the mouth; in some cases, it can also be secondary infection in the tumor. Rapid hyperplasia can also occur in the second growth period of infants, i.e., at 4 to 5 months of age. It usually enters a period of quiescent regression after 1 year. The regression is slow, and the lesions change from bright red to dark purple and brown, and the skin may be maculopapular. According to statistics, about 50% to 60% of patients in 5 years completely subside; 75% in 7 years to subside; about 10% to 30% of patients can continue to subside until about 10 years of age, but may be incomplete subsidence. Therefore, the so-called complete regression period is generally between 10 and 12 years of age. After the complete regression of large hemangiomas, there may be localized pigmentation, shallow scars, and signs of skin atrophy and ptosis.