About Childhood Cancer: types of childhood cancer

Childhood cancer is not a single disease - there are many different types. Compared with adult cancers they tend to have different histologies and occur in different sites of the body.

Leukaemia
Leukaemia is the most common cancer of childhood. The body produces lymphocytes to protect the body from infection, in leukaemia these cells do not mature properly and become too numerous in the blood and bone marrow. Leukaemias may be acute or chronic. The most common type is acute lymphoblastic leukaemia (ALL). There are a number of other less common acute types which may be grouped together as acute non-lymphoblastic leukaemia (ANLL), this includes acute myeloid leukaemia (AML).

Brain Tumours
Brain tumours are the most common solid tumour of childhood. Some are benign others are malignant. There are a number of different types of brain tumour; how they are classified depends on the histology and location within the brain.

Neuroblastoma
Neuroblastoma is one of the most common solid tumours of early childhood usually found in babies or young children. The disease originates in the adrenal medulla or other sites of sympathetic nervous tissue. The most common site is the abdomen (near the adrenal gland) but can also be found in the chest, neck, pelvis, or other sites. Most patients have widespread disease at diagnosis.

Retinoblastoma
Retinoblastoma is a rare tumour of the eye which develops in the cells of the retina, most patients are under 5 years old. Sometimes only one eye is affected (unilateral-retinoblastoma ), but in about two fifths of patients both eyes have the disease (bilateral-retinoblastoma ). Some cases are known to be hereditary.

Wimls' Tumour
Wilms' tumour is a cancer of the kidney which is very different to adult kidney cancer. Most patients are under 5 years of age at diagnosis, though Wilms' tumour is sometimes seen in older children and occasionally in young adults. In most cases only one kidney has disease (unilateral-Wilms' Tumour); but in some cases both kidneys are affected (bilateral-Wilms' tumour). A small minority of cases are known to be hereditary. Other less common kidney cancers in children include malignant rhabdoid tumours and clear cell sarcoma. Treatment for these is usually similar to that for Wilms' tumour.

Hepatoblastoma
Childhood liver tumours are rare. There are two main types of liver cancer; hepatoblastoma and hepatocellular carcinoma. Liver cancer can be found in children of all ages; Hepatoblastomas are more common in patients aged under 3 years, while hepatocellular carcinomas are usually found in patients aged under 4 or between the ages of 12 and 15.

Hodgkin's Lymphoma
The lymphatic system helps the body fight infection. There are two main types of cancer associated with the lymphatic system: Hodgkin's Disease and Non-Hodgkin's Lymphoma (NHL). Both are rare in children aged under 3, and are more common in older children and adults. More boys than girls have childhood Hodgkin's disease.

Soft tissue Sarcoma
Childhood soft tissue sarcomas account for approximately 10% of all childhood cancers. About half of all childhood soft tissue sarcomas are rhabdomyosarcoma, which arises from skeletal muscle, these are most common between the ages of 2 and 6. The other soft tissue sarcomas of childhood include a wide range of different histologies including fibrosarcoma, leiomyosarcoma, liposarcoma, schwannoma, soft tissue Ewing's / peripheral neuroectodermal tumours, synovial sarcoma and many other types. These non-rhabdo sarcomas are more common in adults, but these tumours usually behave quite differently in children compared to the same tumours in adults.  

Osteosarcoma
Osteogenic Sarcoma (osteosarcoma) is a bone forming cancer. It is the most frequent type of bone tumour and is most common between the ages of 15 to 25. Over 90% of tumours are located in the metaphysis (the growing ends of the bone), the most common sites are the bones around the knee which account for 80% of cases. Osteosarcomas vary greatly in radiological and pathological features and therefore needs careful diagnosis to differentiate this from other bone tumours. Most are high grade intramedullary osteosarcomas, about 5% are low grade lesions, some are secondary osteosarcomas (for example those caused by radiation therapy).

Histiocytosis
Langerhan's Cell Histiocytosis (also known as Histiocytosis X) is a rare disease. It is not really a cancer, though it may behave like one in some respects. Histiocytes are normal cells found throughout the body, in this disease abnormally large numbers are found. LCH is more common in children but it is often seen in adults too. The disease will be classed as either single-system or multi-system depending on how many of the body's systems are effected.

Source: http://www.cancerindex.org/ccw/guide2c.htm