Cancers can be classified based on the tissues in which they originate. Sarcomas are cancers that originate in mesoderm tissues, such as bone or muscle, and cancers arising in glandular tissues (e.g. breast, prostate) are classified as adenocarcinomas. Carcinomas originate in epithelial cells (both inside the body and on its surface) and are the most common types of cancer (~85%). Each of these classifications may be further sub-‐divided. For example, squamous cell carcinoma (SCC), basal cell carcinoma (BCC), and melanoma are all types of skin cancers originating respectively in the squamous cells, basal cells, or melanocytes of the skin.