Unlike other cancers, the vast majority of skin cancers have no potential to spread to other parts of the body (metastasize) and become life-threatening. There are two major types of skin cancer: basal cell carcinoma (the most common) and squamous cell carcinoma (the second most common). Melanoma is also a form of skin cancer but is far less common, though more dangerous, than the other two varieties.
The definition of backfill is material used to refill a hole, usually what was previously dug out of the hole. Dirt and gravel are examples of backfill. Backfill is defined as to return soil and other materials to a hole after it was dug.
1 The material that has been used to refill an excavation. ( 2 US) Reserve support personnel. ( 3 US) That which backfills; a replacement. ( 4 literature) Material in a story set earlier in the past, providing history or context for the current action.  backfill bias.