What is a rhabdoid tumour?
Rhabdoid tumours are rare but highly malignant tumours that occur mostly in young children. Rhabdoid tumours can occur in various parts of the central nervous system as well as in other parts of the body. In the brain, rhabdoid tumours can arise in the cerebral hemispheres, ventricles, suprasellar region, pineal gland, cerebellar hemispheres, cerebellopontine angle, and brain stem. See the page entitled “Overview of the Brain” to find out more about different parts of the brain. Rarely, rhabdoid tumours can occur in the spinal cord.
Rhabdoid tumours look a lot like rhabdoid tumours on CT and MRI. It is not possible to tell the difference between these two types of tumours using these imaging tests. The only way to determine that a tumour is really a rhabdoid tumour is to do a biopsy and a specific test called BAF47 staining.
What causes rhabdoid tumours?
Rhabdoid tumours can sometimes arise as part of a rhabdoid tumour predisposition syndrome. This means that some children are predisposed to developing this type of tumour. Most children with this type of tumour have a mutation or loss of a gene called INI1/hSNF5. The specific function of INI1 and its role in malignancy are not entirely clear. However, loss of INI1 expression is seen in almost all rhabdoid tumours. In some children with rhabdoid tumours, mutation or loss of INI1 is also detectable by a staining test on a biopsy sample.
Because rhabdoid tumours occur in infants and very young children, some researchers have suggested that these tumours could arise early in development, from the stem cell or germ cell stage.
How many other children have rhabdoid tumours?
Rhabdoid tumours occur in one to two out of every 100 children who have brain cancer. However, this type of tumour is most common in children under the age of three years. Rhabdoid tumours occur in 10 out of every 100 children under age three who have a tumour of the central nervous system.
Rhabdoid tumours usually present around age two. It is rare for this type of tumour to present in children older than age six years, although some have been reported in teenagers and even in adults.
What are some medical symptoms of rhabdoid tumours?
Symptoms can vary depending on the age of the child, and the location and size of the tumour. Infants may present with nonspecific signs of fatigue, vomiting, or failure to thrive. The child may tilt his head to the side. One non-specific symptom of increased cranial pressure is called cranial nerve 6 palsy, which is a paralysis of the sixth cranial nerve which leads to problems with moving the eye. In young children, a rapidly growing head size may be a sign of a fast growing tumour.
Children with rhabdoid tumour in the posterior fossa area of the brain may present with symptoms related to hydrocephalus: early morning headaches, vomiting, and lethargy. They may have problems with motor coordination.
Children older than three years may present with headache or hemiplegia, which is paralysis of one side of the body.
Because rhabdoid tumours are highly malignant, children usually only have progressive symptoms for days or weeks before diagnosis. It is unusual for symptoms to have been present for more than a few months.