The cause of skin cancer is not fully understood, and its occurrence may be related to long-term stimulation by excessive sun exposure, radiation, arsenic, tar derivatives, etc. Skin cancer is divided into squamous cell carcinoma and basal cell carcinoma, which have slightly different symptoms, sites of development and metastasis. Comparison of the two: The age of onset of squamous cell carcinoma is usually 30-50 years old, while basal cell carcinoma is more frequent above 50 years old. The former has fast onset and rapid growth; the latter is slow. Squamous carcinoma occurs in the lower lip, tongue, nose, vulva, mostly in the junction point of skin mucosa, ulcers with elevated, red and hard edges, annular and cauliflower-like appearance, with significant peripheral inflammatory reaction and mostly regional lymph gland enlargement. Basal cell carcinoma is usually found in the orbit, inner canthus, nose, cheek, forehead, and back of the hand; the ulcer margin is waxy, nodular, and rolled up, and the inflammatory reaction is mild or absent, and metastasis is rare, mainly infiltrating into deeper tissues. Squamous cell carcinoma originates from epidermal spiny cells and usually occurs in sun-exposed areas of the skin. The incidence of squamous cell carcinoma is second only to basal cell carcinoma and occupies the second place among skin cancers. It can occur in any normal tissue or in pre-existing actinic keratoses, mucosal leukoplakia or burn scars. There are approximately 80,000 to 100,000 new cases in the United States each year. The disease often transforms from keratosis pilaris, mucocutaneous leukoplakia, and their precancerous counterparts. Growth is rapid, with tumors initially appearing as erythematous papules or plaques with a scaly or crusty surface, which may become nodular or verrucous. In some cases, the lesions lie mainly below the level of the surrounding skin and eventually ulcerate or erode the surrounding tissue. The percentage of squamous cell carcinoma metastases at sunburned sites is low. However about 1/3 of tongue or mucosal lesions have metastasized prior to diagnosis. The differential diagnosis includes many benign and malignant lesions, including basal cell carcinoma, keratoacanthosis, actinic keratoses, common warts, and seborrheic keratoses. Biopsies must be performed. Some are nodular or cauliflower-like, with less invasion to the depths and a mobile base; others are butterfly-like, with more pronounced infiltration to the depths, more destructive, and often involving the bones. Squamous cell carcinoma is often accompanied by purulent infection with malodor and pain. Regional lymph node metastasis is mostly seen. The development of squamous cell carcinoma is fastest at the mucosal skin junction, and those with mucosal development are more likely to metastasize. In conclusion, early complete resection has better prognosis with less damage. Treatment is the same as basal cell carcinoma, but close follow-up should be performed because squamous cell carcinoma has a higher risk of metastasis. Squamous cell carcinoma in the lip or other mucosal skin junction should be surgically excised, but is more difficult to heal. As with basal cell carcinoma, recurrent cases can be treated with Mohs surgery. Early symptoms of basal cell carcinoma may appear as yellowish or pinkish nodules slightly above the skin surface, with smooth surface and dilated capillaries, hard texture, often without pain or pressure. If the lesion is located in deeper surface, after a long development stage, scaly flakes will appear on its surface, followed by repeated crusting and debridement, surface erosion and blood oozing; when the lesion continues to increase, a superficial ulcer will be formed in its center, with uneven edges, resembling worm erosion. Some of them have warty elevations, and then break down into ulcer foci that are irregular, with elevated edges, resembling craters, and uneven bottoms, with slow growth. Metastases are rare, but first occur as shallow ulcers with translucent nodular elevations, and then gradually expand and erode surrounding tissues and organs, becoming erosive ulcers. The diagnosis of squamous cell carcinoma and basal cell carcinoma ultimately depends on biopsy, which requires the diagnostician to have enough experience to identify lesions suspected of malignancy and to differentiate them for different treatment plans. Surgery is the preferred treatment for skin cancer, and the cure rate can reach 90% to 100% with proper surgical excision treatment. The skin incision should be made at a distance of 0.5-2 cm from the tumor and should be deep enough to make a wide excision as possible. Both basal cell carcinoma and squamous carcinoma are sensitive to radiation therapy, i.e., the efficacy is very good. Before determining the radiotherapy, the patient’s age, gender, tumor history, anatomical site, and the final cosmetic effect achieved by cure and recurrence must be considered.