Metastatic cancer is not the same as stage 4 cancer, according to the National Cancer Institute. Metastasis means that the cancer has spread from its original site to other sites, according to the American Cancer Society. What precisely the stage designation means depends on the type of cancer.
Stage 4 means that the cancer is metastatic and has spread to sites distant from the original tumor, notes the American Cancer Society. However, stages 1, 2 and 3 also sometimes mean that the cancer has spread to other organs and lymph nodes. These structures are not as distant as the organs affected in stage 4 cancer.
Cancers such acute myeloid leukemia do not follow standard staging because they are blood cancers and thus are not localized, according to Cleveland Clinic. Brain cancer is dangerous but does not metastasize or does so rarely, notes the National Cancer Institute.