Today, there are more than 100 different types of cancer. Cancer types are determined based on cancer spreading characteristics, the types of cells where the cancer shows up and where they are located. Cancers that are limited to one region are called in situ, and cancers that have spread are called invasive cancer. Cancer can show involvement in different cell types. For example, cancer that has involvement in small lung cells is called small cell cancer, cancer that has involvement in squamous cells in the skin or oesophagus is called squamous cell cancer. Finally, cancer types are named according to their location in the body. For example, if cancer is in the breast, is called breast cancer, if cancer is in the lung, lung cancer, if cancer is in men’s prostate area, prostate cancer, and if cancer is in skin, is called skin cancer. By using these three criteria, the type of cancer is determined in detail. For example, the type of cancer that does not spread at a location and spreads to the basal cells in the skin is called in situ basal cell skin carcinoma.