Screening is a procedure done in the general population, like a colonoscopy or Pap smear, that looks for pre-cancerous cells, cysts or lesions. Screening looks for irregularities before cancer has a chance to grow, in order to prevent disease. Early detection, on the other hand, is a method of finding cancer in its earliest stages, when intervention can be successful and may help prevent mortality. Mammograms are a well-known early detection tool for breast cancer. There is no screening or early detection test for ovarian cancer. Some people think the Pap smear can detect ovarian cancer, but it cannot. It can only screen for cervical cancer. This is one of the reasons why ovarian cancer is the deadliest of all gynecologic cancers; symptoms typically only appear, and thus ovarian cancer is often only diagnosed, when the disease is in late stages and the cancer has spread. When experts in the field of ovarian cancer talk about early detection, they are working to better understand the origins of the disease (such as discovering that lesions have been found on the fallopian tubes in ovarian cancer patients) and where else in the female reproductive tract these precancerous cells, that will later form tumors in the ovaries, might present. But this type of learning takes time — it could take decades – and so scientists are also focused on discovering better treatments for those who need effective therapies today.