Skin cancer stages are part of a vital system that is used to determine prognosis, survival, and treatment plans. Multiple variables factor into stage determination, and usually varies among cancer types. The most commonly used classification system is the TNM system, which looks at particular tumor characteristics and grades them X,0,1,2,3, or 4 with the larger numbers indicating increasing category severity. T stands for tumor and includes things like the tumor’s location, size, and depth. N stands for node, and describes whether the cancer has spread to the lymph nodes, locally or farther away. M is for metastasis, which is the spreading of cancer to distant parts of the body. With the values for T, N and M determined, those are combined and an overall stage grouping is assigned.