Formation and growth of tumorous cells
- Solid tumors are formed from cells with altered genetic material, causing it to respond differently to the host's growth regulators and leads to uncontrolled growth.
- Early tumor cells can obtain enough nutrients from existing vasculture and so the proliferation rate is regular, producing growing spheroid of cells expanding at high speed.
- As the tumor grows, the amount of nutrients that is able to diffuse through to the center decreases, and so the central cells become so deficient that division ceases, forming a region of dead cells known as a necrotic core. As the spheroid continues to develop, the outer most layer of cells become roughly constant in size leading to a phase of linear growth.
- In order to grow beyond this limit, tumors require blood supply. This is achieved by the secretion of tumor angiogenesis factor (TAF), which diffuses across the tissue between the tumor and blood vessel, activating angiogenesis.
- Metastasis refers to spread of the cancer, and occurs when cancer cells break away from the primary tumour and enter the bloodstream or the lymphatic system where they are carried to other parts of the body. When a new tumour forms at a site away from the primary site, it is known as a "metastatic tumour".
