Basal cell carcinoma mostly occurs after the age of 30, with a peak at the age of 70, and is most common on the head and face, especially on the nose, eyelids and cheeks. There are ten types of basal cell carcinoma, and I will tell you their characteristics below. 1.Nodular ulcerative basal cell carcinoma is the most common, accounting for 50%-54% of basal cell carcinoma, and the damage is single. Scleroderma-like basal cell carcinoma, also known as limited scleroderma-like basal cell carcinoma, is rare and accounts for only 2% of basal cell carcinoma. It occurs mostly in young people, but also in children, and is often solitary, usually on the face, forehead, cheekbones, nose and eye canthus, especially on the cheek, neck or chest, and appears as flat or mildly depressed yellow-white waxy to sclerotic infiltrative plaques, irregular or plucked, from a few millimeters to occupying the entire forehead, grayish white to yellowish, with smooth surface, permeable to capillary dilatation and hard to touch. Similar to limited scleroderma, lack of rolled up pearly edges, no ulcers and crusts, the edges are often indistinct, and the lesions develop slowly. 3.Fibroepithelioma-like basal cell carcinoma appears as one or several elevated nodules, slightly tipped, hard to touch, with smooth surface and mild redness, clinically similar to fibroma, usually in the lower back, with rare ulcer formation, clinically similar to fibroma. 4.Nevus-like basal cell carcinoma syndrome, also known as basal cell nevus syndrome, is an autosomal dominant disorder with low ectopic rate, in which a raised, hard, smooth nodular swelling appears on the skin, which may be of normal skin color or with mild pigmentation. In childhood and, at the latest, in adolescence, hundreds of small skin nodules appear, which gradually increase in number and size during the “nevus-like” phase and are irregularly distributed over the face and trunk. In adulthood, many basal cell carcinomas often break down, and the disease sometimes progresses to the “neoplastic” stage in later years, when some basal cell carcinomas, especially facial damage, become invasive, destructive and crippling, and occasionally even cause death due to invasion of the orbit first and then the brain, and can also metastasize to the lungs. ～In half of adult patients, many small depressions of 1~3 mm in diameter appear on the palmoplantar area, often occurring between 11 and 20 years of age, as stenotic basal cell carcinoma. In addition to skin lesions, almost all patients present multiple skeletal and central nervous system abnormalities, including, for example, odontogenic angular cysts of the jaws, rib abnormalities, scoliosis, mental retardation and cerebral sickle calcification, with several cases reported, and also cerebellar neurogenic osteoblastoma, maxillary or jaw fibrosarcoma, and enucleated cell tumors occurring in jaw cysts. The lesions consist of dense basal cell carcinoma nodules with scattered acne and striated atrophic areas, and the damage does not increase with age. 6.Pigmented basal cell carcinoma is the one with pigmentation among all types, accounting for 6% of basal cell carcinoma. It is different from nodular ulcer type only in that the lesions are brown or dark black, and sometimes it is easily misdiagnosed as malignant melanoma, with clinical characteristics similar to nodular type, only accompanied by different degrees of pigmentation white gray to dark black, but not uniformly, the marginal part is often darker, and the central part is dotted or reticulated. Superficial basal cell carcinoma is rare, mostly seen in men, with an early age of onset and very little head, accounting for 9% to 11% of basal cell carcinoma, often occurring on the trunk, especially the back and chest, but also on the face and extremities, with one or several mildly infiltrative erythematous scaly patches, with thin surface epidermis and slightly elevated linear border, often with superficial ulcers and scabs in the central part, which can Eczema or psoriasis-like changes, slowly increasing in size to the periphery, with clear boundaries, often surrounded by thin thread-like pearly edges, with small superficial ulcerated crusts visible on the surface of the lesions, leaving smooth atrophic scar after healing. 8.Flat scar type It is quite rare, often occurs in the face, and the damage is superficial nodular plaque with slow growth. The characteristic of this type is that when basal cell carcinoma expands slowly in all directions, the tumor cells in the central part gradually disappear and form a scar, just like a forest fire spreading in all directions but the center extinguishes itself, so it is also called wildfire type, and its expanding edge is very aggressive. 9.Cystic basal cell carcinoma is relatively rare and is caused by the degeneration of the central part of the carcinoma and the formation of a single-compartment cyst, which is usually blue-gray in color. Bazex syndrome was firstly reported by Bazex et al. in 1966. The disease is dominantly inherited and its main features are firstly follicular skin atrophy with dilated “chiseled ice marks” on the extremities, followed by multiple small basal cell carcinomas on the face of children, youth or adolescents. Anhidrosis and/or generalized hypohidrosis and congenital scarcity of hair on the head and other areas.