Most cancers correspond to one of five stages, ranging from 0 (zero) to IV (Roman numeral 4) according to the National Cancer Institute. Stage IV is the last, indicating the cancer has spread to a distant part of the body from the organ or tissue in which it began.
Stages I, II and III are assigned depending on the size of the original tumor and whether the cancer has spread to nearby lymph nodes, tissues or organs. Stage 0, according to the NCI, indicates carcinoma in situ, meaning that abnormal cells are present but have not spread. Carcinoma in situ is not cancer, but it may progress that way, which is why some refer to it as "preinvasive cancer."