Basal cell carcinoma is the most common skin cancer among all and squamous cell carcinoma is the second most. Precancerous lesions include actinic keratosis and leukoplakia.  Squamous cell carcinoma in situ (formerly called Bowen disease) and keratoacanthoma are sometimes difficult to differentiate squamous cell carcinoma which potentially metastasizes. Melanoma is referred as "cancer of a mole." All these can be clinically differentiated by looking and using a dermoscopy which is a device to examine a skin lesion with strong light, but it is impossible to tell the diagnosis for 100% certainty without examining the tissue sample with a biopsy or a surgery. We encourage the patients to take a biopsy or a surgery if the lesion may be malignant. After sending the tissue to an outside laboratory, the slide is examined inside the clinic with a pathology microscope. Only the difficult cases are sent to an outside skin pathology laboratory. Mohs surgery is available for basal cell carcinoma and squamous cell carcinoma, which preserves the normal skin while taking all the malignant lesion by performing the on-the-site pathology examination inside the clinic. This method is common countries outside Japan, but our clinic is the only medical facility in Japan which performs this mode of operation. Regular surgery (non-Mohs surgery) is also possible for most skin cancers since the director of the clinic is board-certified both in dermatology and plastic surgery. Those who have been diagnosed as skin cancer and suggested to excise with wide margins can consult us if a reference letter, a pathological report and a glass slide are available.