Lymphomas are cancers of the lymphoid tissue, which is part of our body's immune system. 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.
The description and classification of the various types of non-Hodgkin lymphoma has developed over the years as more has been learnt both about the immune system and the cancers themselves. The most recent classification divides non-Hodgkin lymphoma into some fifteen different tumour types. Each of these will have different patterns of behaviour and may need different approaches to treatment.
ALK positive non-Hodgkin lymphoma or anaplastic large cell lymphoma is a relatively uncommon form of NHL, accounting for about 3% of all cases in adults. It is more common in children [10-30%]. They occur mainly in the first 30 years of life and are more common in men than women. It is a T-cell lymphoma that under the microscope appears to be made up of large lymphoma cells. These cells usually make large amounts of a protein called ALK [anaplastic large-cell lymphoma kinase]. Special stains on the biopsy tissue can detect this. The reason for this is usually a genetic change affecting the piece of genetic code that carries the instructions for ALK on chromosome 2. There are a variety of genetic changes that swap a bit of chromosome 2 with other chromosomes e.g. chromosome 5 – t(2;5).
Most types of NHL usually appear as painless swellings in the neck, armpit or groin, caused by enlarged lymph nodes. ALK positive non-Hodgkin lymphoma often affects tissues out of the lymphatic system such as bone, liver or skin. The precise symptoms caused by the cancer will vary with which organs are affected but some general symptoms which 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. 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. Most cases of this lymphoma are treated with combination chemotherapy. On the whole they have a better prognosis than other high-grade lymphomas with 80% of patients still alive at 5 years.