CUP patients also are benefiting from advances being made in life-prolonging treatments for people with advanced cancer. In truth, the answer remains a mystery. But researchers do have theories. But that's all conjecture because we have no way of determining what happens to the primary. When a primary tumor isn't obvious, some degree of diagnostic detective work is required by the patient's oncologist, who works closely with a hospital clinical pathologist.
Clues come from several sources.
These tumors retain the microscop-ic structure of the tissue in which the tumor originated, which often makes it possible to identify the source of the primary tumor. The location of the metastatic tumor in the body can provide a clue about the tumor's possible origin. For example, patients who have metastatic cells in lymph nodes of the chest or neck, particularly if they are smokers, are often thought to have lung cancer. The presence of metastatic cells in lymph nodes of the armpit of females suggests breast cancer. Often, though, the microscopic structure of metastatic tumors bears little resemblance to that of a particular organ.