Understanding Pediatric Cancer (1): Types of Childhood Cancers

I recently received terrible news from my sister that her friend's niece had been diagnosed with Acute Lymphoblastic Leukemia. As this is the population of children that I had worked with for the last 3 years and whose data I had toiled many nights trying to understand and write for my thesis, I had vested interest in understanding more.

My sister had a lot of questions about childhood cancer, which I thought would be best answered with a series of posts based on my research, which is in no way exhaustive. I hope what I have learnt in my graduate training will be of help to you :)

*Note: The following information has been adapted from my own research and was therefore not written by a medical professional. The terms 'child' or 'children' refer to individuals below the age of 21 years old.

Lesson 1: Types of Childhood Cancers

Cancer in childhood is relatively rare. Children with cancer often present with symptoms of fever, fatigue, pain, bruising, etc and the severity of the symptoms is dependent on the type of cancer.

These symptoms are also non-specific and can easily be mistaken for a less serious illness, thus making it hard for doctors to recognize and diagnose the disease.

Despite extensive research, the cause of childhood cancer is still not well established. Although it is common for parents (especially mothers) of children with cancer to blame themselves for not taking care of their children, in actual fact they are not the cause of their child's illness. There was one study that found no genetic or environmental factors that were related to cancer (even as far as to say it seemed to happen randomly). It is hoped that further research and greater medical advancement would give us an answer in future.

There are many types of cancer in children and its classification is often done by histology or type of cells involved rather than by organs as is used in adults. The most common type of cancer in children is leukemia (40.8% in Singapore), followed by other solid tumors such as neuroblastoma, lymphoma, etc.

1) LEUKEMIA

Leukemia is an increase in malignant cells occurring in the bone marrow. These malignant cells replace normal bone marrow cells and then subsequently enter the blood stream. Leukemia later leads to a reduction in the number of white blood cells and platelets in the blood, which lowers the immunity.

The child may therefore show infection-like symptoms such as fatigue, bleeding, bone pain, bruising or irritability. As these symptoms are non-specific, a blood test is required to make a diagnosis of leukemia.

The most common type of leukemia in children is Acute Lymphocytic Leukemia (ALL) (80% of all leukemia cases) while Acute Myeloid Leukemia (AML) and Chronic Myeloid Leukemia constitutes the rest. Prognosis is generally good as the 5-year survival rate for ALL is approximately 80%.

2) BRAIN TUMORS

Photo credit: hopkinsmedicine.org

Brain tumors are the most common form of Central Nervous System tumors, and its severity ranges from relatively benign to those that are highly malignant with poor prognosis.

Tumors in the brain can affect the balance and eye movements of pediatric patients. They can also cause a blockage in the flow of fluid between the brain and spinal cord resulting in a rise in intracranial pressure, which may cause severe headaches and vomiting.

The most common type of brain tumor in Singapore is medulloblastoma, which are malignant tumors derived from primitive embryonal tissue. The survival rate for medulloblastoma is approximately 60-70%, which is less than that of children with ALL. This is because treatment for brain tumors is generally more challenging and the brain is more susceptible to late treatment effects like brain damage and learning disabilities.

3) NEUROBLASTOMA


Credits: biota.utoronto.ca

Neuroblastoma originates from 2 sources: i) neural crest tissue in the adrenal gland, ii) sympathetic nervous tissue in the chest and abdomen.

The most characteristic symptom of neuroblastoma is the presence of a mass at the abdomen of the patient. Patients often complain of abdominal pain, vomiting, constipation and loss of appetite.
Due to the nature of the disease, prognosis is better in children younger than 12 months and significantly poorer in children older than 12 months. Even with intensive treatment, the survival rate is approximately 20-30%.

(Remember the girl with Neuroblastoma that I blogged about earlier? It is nothing short of a miracle that she is in remission after much prayer and the medical care of her doctors.)

4) LYMPHOMAS

Photo credit: India Cancer Hospital

There are 2 main types of lymphomas: i) Hodgkin’s disease and ii) non-Hodgkin lymphoma.

Lymphomas are tumors that arise from the lymphoid tissue, which is part of the body’s immune system. Typically, the tumor leads to enlargement of the lymph glands and may also spread to other organs like the liver, spleen or bone marrow. There may be pain at the site of the cancer.

In order to make a diagnosis of lymphoma, diagnostic imaging tests and biopsy of the affected tissue are required. Prognosis is also generally good.

5) MALIGNANT BONE TUMORS

Photo credit: Danis Foundation

The most common malignant bone tumors are Osteosarcoma and Ewing’s sarcoma. Sarcomas are cancers that develop in the supporting structures of the body like bone or soft tissue.

Both are most commonly presented in children ages 10-15 years, which is a period when rapid bone development occurs (although tumors can appear in young children as well). The characteristic symptom of malignant bone tumors is persistent and localized bone pain that is typically at the leg or arm, after which a mass at the affected site is detected.

6) OTHER TUMORS

Other tumors include: i) Kidney tumors (e.g. Wilms’ tumor), ii) Rhabdomyosarcoma, iii) Retinoblastoma (tumor of the eye in infants), iv) germ-cell tumors and v) liver tumors.


References:
Dixon-Woods, M., Young, B. & Heney, D. (2005). Rethinking experiences of childhood cancer: A multidisciplinary approach to chronic childhood illness. Open University Press: Maidenhead.

Eiser, C. (2004). Children with Cancer: The Quality of Life. Lawrence Erlbaum Associates: United States of America.

Health Promotion Board. (n.d.). First Report of the Singapore Childhood Cancer Registry 1997 – 2005. Retrived August 5, 2009, from www.hpb.gov.sg/data/hpb.home/files/Monograph v1.06.pdf.



Continue to >> Understanding Pediatric Cancer (2): Treatment

Update: If you'll like to find out the results of my research, my complete thesis can be found on the NUS Scholar Bank (Part 1 & Part 2) =)

This post is part of my series on My Pediatric Cancer Research. 

Read on to learn more about childhood cancer and its impact.