The cause of cancer in patients remains a mystery. Various theories and assumptions do not give confidence in understanding the cancer process. Until the etiology of cancer is studied, we will not be able to move forward despite the development of pharmaceutical technologies and innovative treatments. To solve this problem, it is intended to use all data related to cancer development, even if they have no obvious link to the disease. Even when a cancer cell appears and starts creating its pool of altered cancer cells we don't know. Doctors diagnose cancer, when the tumor reaches certain sizes and disorders the function of the organ. The number of cancer cells increases very quickly. The factors that accelerate this reproduction of cancer cells are many, which means that we still do not see the true cause. The cancer cell retains the features of the original cell to varying degrees from pronounced similarity to almost complete loss of healthy cell properties. The more the foreign cell is altered, the faster it grows and the prognosis for the patient is deteriorated. The most worrying thing is that the incidence of cancer is increasing, which means the cause is not found. Cancer deaths remain high. This article discusses the case of a patient having a limb amputated for cancer (foot skin cancer). During a 10- year study of bone marrow from the femur, for the first time, bone marrow was obtained from the femur of a patient with cancer. The findings could help researchers and doctors better understand the cancer process and look at the problem differently.