In less advanced stages (stages I and II), cancer of the colon (large intestine) does not extend outside of the large intestine, and cancer cells are not seen under the microscope in the lymph nodes that lie near the large intestine. Surgery alone is used to treat these early stage cancers; chemotherapy is reserved for cancers at more advanced stages. Despite the fact that cancer cells cannot be found with ordinary testing of the lymph nodes in early stage colon cancers, the cancer recurs after initial surgery in up to half of the patients with stage II cancer. This suggests that some cancer cells are actually hidden in the lymph nodes but are just not detected by the tests available. Researchers have looked for other ways to detect these hidden cells, but none of these have proven reliable so far.