ABSTRACT
There is now considerable evidence based on molecular and biomedical studies that the leukemias, lymphomas and myelomas each originate in a single cell in the bone marrow, thymus or peripheral lymphoid tissue. The reason why a single cell is prone to become a cancerous (malignant) cell is unclear. Once the cell has become malignant, it divides and forms daughter cells with an identical make-up. This process is sometimes referred to as a clonal expansion. Why this malignant clone should escape from normal body controls is unclear, though there are a number of interesting, and perhaps competing, hypotheses and we will discuss these shortly.
