i've had five BCCs (basal cell carcinomas) removed. they are the most benign skin cancer, usually presenting as a small sore that won't heal. some have 'rolled, pearly borders' with ulcerated centers... not all do. common on the ears, shoulders, face and sun-exposed areas.
more concerning than BCCs are SCCs (squamous cell carcinomas), usually presenting first as a pre-cancer called AKs (actinic keratoses). AKs are often 'rough', scaly, sometimes reddened areas on sun-exposed skin that progress to ulcerations if left untreated. not all AKs progress to SCCs, and not all SCCs present on sun-exposed skin (e.g. SCCs develop in the anal canal due to exposure to HPV, a very common condition in gay men... get an anal PAP!).
worst type is melanoma, an aggressive type of skin cancer that can metastasize rapidly. once mets are found, prognosis is not good.
always check the ABCDEs of any skin lesion. is the lesion Asymmetrical, are the Borders nondistinct and irregular, are the Colors unusual and not skin-like, is the lesion's Diameter relatively large and is it Elevated? if more of these criteria are met, the lesion is more concerning.