Haematological cancers most often begin in the bone marrow where blood is produced. Stem cells in the bone marrow develop into white blood cells, red blood cells, or platelets. Blood cancers occur when uncontrolled growth of abnormal blood cells overtakes the development of normal blood cells and interferes with the regular functions of these cells. Blood cancers fall into three categories: leukaemia, lymphoma, and myeloma.
Leukaemias are blood cell cancers; some leukaemias are fast growing, while others develop slowly. Lymphoma occurs when lymphocytes (infection-fighting white blood cells) develop abnormally and become cancerous. These multiply and aggregate in lymph nodes and other tissues. Among common lymphomas are Hodgkin lymphoma, non-Hodgkin Lymphoma, AIDS-related lymphoma, and primary central nervous system (CNS) lymphoma. Myeloma is a cancer that occurs in plasma cells. Normal plasma cells produce antibodies that fight disease and infection. However, when abnormal plasma cells develop, they interfere with antibody production and lead to reduced immunity.
A solid tumour is an abnormal mass of tissue that usually does not contain cysts or liquid areas. Solid tumours may be benign (not cancer), or malignant (cancer). Solid tumour types are named according to the type of cell they originate from. Examples of solid tumours are sarcomas, carcinomas, and lymphomas. Leukaemias (cancers of the blood) generally do not form solid tumours.
The word tumour does not always imply cancer. In discussing tumours that are malignant (cancerous), however, the term solid tumour is used to distinguish between a localised mass of tissue and leukaemia.
