What is cancer

Cells are tiny building blocks that make up the body's organs and tissues.                                                                                                                                Cells receive signals from the body,telling them when to grow and when to divide to make new cells. This is how our bodies grow and heal.                        These cells can become old,damaged or no longer needed. When this happens,the cell gets a signal from the body to stop working and die. Sometimes these signals can go wrong,and the cell becomes abnormal. The abnormal cell may keep dividing to make more and more abnormal cells. These can then form a lump, called a tumor. But not all tumors are cancer. Doctors can tell if the tumor is cancer by taking a small sample of the cells. This is a biopsy. The doctors will examine the sample  to look for abnormal cells. 

A tumor that is not cancer,a benign tumor may still grow but it will not spread. it will usually only cause problems to other organs if it grows and presses on the organs nearby. 

A tumor that is cancer or a malignant tumor can grow into nearby tissue.

Sometimes the cancer cells will spread from where the cancer started to other parts of the body. this initial site is known as the primary site. They usually travel around the body in blood or lymph fluid which is part of the lymphatic system. When these cancer cells reach another part of the body, they may grow and form another tumor. this is called secondary cancer or metastasis. 

Some types of cancers can in fact start from blood cells. Abnormal cells can build up in the blood, and sometimes the bone marrow. This is where blood cells are made. These cancers are called blood cancers.