Basal Cell Cancers or BCC is the most common skin cancer. Luckily this is the least dangerous as it does not usually metastatise. Left too long it keep growing. This will ulcerate and start to bleed. The most common reason for this is sun damage due to exposure to UV radiation from the sunlight. 

There are three common types of BCC I see, Superificial BCC, Nodular BCC, Morpheiform or sclerosing BCC. Most of these do not have pigment in them but these can be pigmented and can be alarmingly dark as well.