One of the most important cells in our immune system is a type of white blood cell called a lymphocyte. There are two types of lymphocytes: 'B-cells' and 'T-cells'. All lymphocytes are produced in the bone marrow and start life as young, immature cells called stem cells. Some lymphocytes continue their development in the bone marrow or lymph nodes and these are called B-cells but others move to the thymus gland and they are called T-cells. There is also another group of white cells that make up our immune systems called natural killer or NK cells. These appear to recognise and destroy foreign cells by a variety of ways independent of T or B cells. Any of these cells can become cancerous and give rise to either a leukaemia or a lymphoma.

Lymphoma means a cancer of the lymph system. This includes the lymph glands, the spleen, the liver as well as the bone marrow. The word leukaemia is used when there is a high white count in the blood. Also, if you have a lymphoma where lots of cells are spilling out into the blood, you can describe it as a leukaemia or it being in ‘leukaemic phase’.

NK leukaemia/lymphoma is a rare disease where the cancerous cell is very similar to the normal NK cell. It mainly affects the young and is more common in Asians than Caucasians. The main organs affected are the bone marrow and blood, liver and spleen. Because much of the disease is in the blood and little disease is in the lymph nodes it tends to be called a leukaemia. Sometimes in some patients there is little disease in the blood or marrow but instead lumps of disease appear outside of the lymph system. This is called extranodal NK lymphoma and mainly affects the nose, skin, or gut. There is also overlap between these 2 diseases. The precise symptoms caused by the cancer will vary with which organs are affected but some general symptoms that may be present include night sweats, unexplained fever, loss of appetite, weight loss or tiredness.

The diagnosis is made by a small operation, called a biopsy, which takes away a sample of the suspect lymphatic tissue to examine the cells under the microscope. The cells in the blood also have a typical appearance under the microscope and a characteristic pattern of markers on the surface of the cell that can be identified using specialised tests. Additional tests, including blood tests, x-rays, scans and bone marrow samples, are then used to get more information about the lymphoma and to see if it has spread elsewhere in the body. This is important in deciding treatment. The majority of these cases have an aggressive clinical course with poor responses to therapy and frequent relapses. It is however important to know that there are some more chronic and slow-growing forms of this disease that have a much better prognosis.