Leukemia
Cancer of the blood where white blood cells are produced in excessive amounts and do not work properly. Read more

Leukocyte
A white blood cell of the immune system, which helps the body fight infectious diseases.

Low immunity
Cancer treatments reduce the patient’s white blood cell count and so compromise the immune system. A lowered immune system is one of the most serious short-term effects of cancer treatments because it makes children more susceptible to infections and illnesses. Infection is the leading cause of serious complications and death of children with cancer. In fact, this is one of the reasons mortality rates [link to world stats page] are so high for children with cancer in poorer nations. Children on treatment run a significantly higher risk of contracting communicable diseases such as colds and childhood illnesses such as chickenpox [link].

Lumbar puncture (LP)
A diagnostic procedure used to sample the fluid surrounding the brain and spinal cord (cerebral-spinal fluid). A needle is inserted into the spinal canal at the lower end of the back and fluid then flows out.

Lymphatic system
The lymphatic system is a complex network of nodes and tiny tubes or vessels that drain fluid from the body's tissues. It is a major component of the immune system, destroying foreign matter and producing antibodies to fight infection. It has three interrelated functions: (1) removes excess fluids from body tissues; (2) absorbs fatty acids and transports fat, as chyle, to the circulatory system; and (3) produces immune cells. Lymph nodes are found in the armpits, groin, neck, mid-chest and abdomen.

Lymph nodes
Hundreds of small oval bodies scattered throughout the body. They act as the first line of defence against infections and cancer.

Lymphoblast
Lymphoblasts are poorly differentiated (immature) blood cells, which, when seen in excess may indicate leukemia. Lymphoblasts are immature cells that typically differentiate to form mature lymphocytes [link]. Normally lymphoblasts are found in the bone marrow but in acute lymphoblastic leukemia (ALL), lymphoblasts proliferate uncontrollably and are found in large numbers in the peripheral blood.

Lymphocytes
White blood cells that kill viruses and defend against the invasion of foreign material.

Lymphoma
Lymphomas generally originate in lymphoid tissue and are the second most common malignancy in young people, accounting for about 17 per cent of new cases and 8 per cent of deaths. The type of lymphoma is determined by the type of cell that makes up the tumour. There are two broad types of lymphoma: Hodgkin disease and non-Hodgkin lymphoma. They are both characterized by abnormal masses in the lymph system.