Embryonal tumours are a type of cancer that develops from embryonic (or fetal) cells in the central nervous system (CNS). The CNS is responsible for all sensory and motor functions in the body, and is composed of the brain and the spinal cord.
Embryonic cells are the cells that humans develop from after fertilisation. Normally, these cells in the embryo differentiate into a specific cell type (such as blood cells and organ tissues) before the eighth week of pregnancy. However, in some cases embryonic cells may be present after birth. They are usually harmless, but in rare instances they may become cancerous.
Embryonal tumours are most commonly found in babies and children under nine years of age. However, they can develop at any age.
Types of Embryonal Tumours
There are six different types of embryonal tumours in the CNS.
Medulloblastomas
Medulloblastomas are the most common type of embryonal tumour, and are the most common type of childhood brain cancer. These tumours often develop in the lower back portion of the brain, known as the cerebellum. The cerebellum is responsible for muscle coordination, posture, balance and movement. This type of tumour is most common in children between the ages of three and nine, with male children having a slightly higher incidence than female children. While many medulloblastomas can be aggressive with a tendency to spread through the cerebrospinal fluid (CSF) surrounding the brain and spinal cord, these tumours can have a good prognosis when caught early.
Embryonal Tumours with Multilayered Rosettes (ETMRs)
Embryonal tumours with multilayered rosettes (EMTRs) are a rare subtype of embryonal tumours that generally occurs in children under three years old. These tumours often begin in the largest portion of the brain, known as the cerebrum, however it can develop in other parts. The cerebrum is primarily responsible for thinking and voluntary movement. Unfortunately, ETMRs are very aggressive, and may not have as good of a prognosis as other embryonal tumours.
Medulloepitheliomas
Medulloepitheliomas are a rare subtype of embryonal tumours that generally develop in children under the age of nine. These types of tumours can develop anywhere in the CNS, including the brain, spinal cord, or nerves located just outside of the spinal column, as well as the eye. Unfortunately, Medulloepitheliomas are very aggressive, and may not have as good of a prognosis as other embryonal tumours.
Atypical Teratoid/Rhabdoid Tumours
Atypical teratoid rhabdoid tumours (ATRTs) are a very rare subtype of embryonal tumours that generally develop in children under three years of age. In most cases, these tumours develop in the cerebellum or brainstem, however they can develop in other parts of the CNS. The cerebellum is the lower back portion of the brain that is responsible for muscle coordination, posture, balance and movement. The brainstem, which is located next to the cerebellum, is responsible for controlling breathing, heart rate, and the nerves and muscles used for seeing, hearing, walking, talking and eating. Unfortunately, ATRTs are very aggressive, and may not have as good of a prognosis as other embryonal tumours.
CNS Neuroblastomas
Neuroblastomas of the CNS are a very rare subtype of embryonal tumours that generally occurs in children under 10 years old, with the average age of diagnosis of 18 months. These tumours develop in the nerve tissue of the cerebrum, or in the layers of tissue that cover the brain and spinal cord, known as the meninges. The meninges have three layers, and acts to protect the CNS. While CNS neuroblastomas can be aggressive, they can have a good prognosis when caught early.
For more information on neuroblastomas, please refer to the Rare Cancers Australia Neuroblastoma page.
CNS Ganglioneuroblastomas
Ganglioneuroblastomas of the CNS are a subtype of CNS neuroblastomas that have both benign (non-cancerous) and malignant (cancerous) parts of the tumour. They usually develop in the meninges of the brain and spinal cord, and can have a good prognosis when caught early.
For more information on ganglioneuroblastomas, please refer to the Rare Cancers Australia Neuroblastic Tumours page.
Some of the information regarding the types of embryonal tumours was obtained from the Childhood Medulloblastoma and Other Central Nervous System Embryonal Tumours Treatment (PDQ) page published by the National Cancer Institute.
Treatment
If an embryonal tumour is detected, it will be staged and graded based on size, metastasis (whether the cancer has spread to other parts of the body) and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you.
Cancers can be staged using the TNM staging system:
- T (tumour) indicates the size and depth of the tumour.
- N (nodes) indicates whether the cancer has spread to nearby lymph nodes.
- M (metastasis) indicates whether the cancer has spread to other parts of the body.
This system can also be used in combination with a numerical value, from stage 0-IV:
- Stage 0: this stage describes cancer cells in the place of origin (or ‘in situ’) that have not spread to nearby tissue.
- Stage I: cancer cells have begun to spread to nearby tissue. It is not deeply embedded into nearby tissue and had not spread to lymph nodes. This stage is also known as early-stage cancer.
- Stage II: cancer cells have grown deeper into nearby tissue. Lymph nodes may or may not be affected. This is also known as localised cancer.
- Stage III: the cancer has become larger and has grown deeper into nearby tissue. Lymph nodes are generally affected at this stage. This is also known as localised cancer.
- Stage IV: the cancer has spread to other tissues and organs in the body. This is also known as advanced or metastatic cancer.
Cancers can also be graded based on the rate of growth and how likely they are to spread:
- Grade I: cancer cells present as slightly abnormal and are usually slow growing. This is also known as a low-grade tumour.
- Grade II: cancer cells present as abnormal and grow faster than grade-I tumours. This is also known as an intermediate-grade tumour.
- Grade III: cancer cells present as very abnormal and grow quickly. This is also known as a high-grade tumour.
Once your tumour has been staged and graded, your doctor may recommend genetic testing, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment is dependent on several factors, including location, age, stage of disease and overall health.
Treatment options for embryonal tumours may include:
- Surgery, potentially including:
- Brain surgery to remove the tumour, or as much of the tumour as possible.
- Surgery to relieve fluid build-up in the brain. Usually this involves inserting either an external ventricular drain or a ventriculoperitoneal shunt.
- Chemotherapy.
- Radiation therapy.
- Targeted therapy, potentially including signal transduction inhibitors.
- Clinical trials.
- Palliative care.
For more information on the treatment options, please refer to the Rare Cancers Australia Treatment Options page.
Some of the information regarding treatment was obtained from the Childhood Medulloblastoma and Other Central Nervous System Embryonal Tumours Treatment (PDQ) page published by the National Cancer Institute.
Risk factors
While the cause of embryonal tumours remains unknown, there are several inherited conditions that may increase the risk of developing this disease, including:
- Turcot syndrome.
- Rubinstein-Taybi syndrome.
- Nevoid basal cell carcinoma (Gorlin) syndrome.
- Li-Fraumeni syndrome.
- Faconi anemia.
Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
Some of the information regarding risk factors was obtained from the Childhood Medulloblastoma and Other Central Nervous System Embryonal Tumours Treatment (PDQ) page published by the National Cancer Institute.
Early symptoms
Symptoms of embryonal tumours may vary between the different subtypes and different age groups.
Children with embryonal tumours may experience the following symptoms:
- Difficulties with balancing and coordination and/or walking.
- Slowed speech.
- Headache, especially in the morning.
- Headache that only goes away after vomiting.
- General weakness and fatigue.
- Seizures.
- Double vision and/or other eye problems.
- Nausea and/or vomiting.
In addition to this, infants and/or young children may also experience:
- Irritability.
- Slowed growth.
- Changes in eating habits.
- Delayed developmental milestones, such as sitting up, walking and talking.
Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned.
Diagnosis/diagnosing
If your doctor suspects you have an embryonal tumour, they will order a variety of tests to confirm the diagnosis and refer you to a specialist for treatment.
Neurological exam
A neurological examination assesses sensory and motor functions, and can generally be done in your GPs office. The doctor may check your vision, hearing, balance, coordination, strength and reflexes, depending on the signs and symptoms you have described. Any problem that is detected in this exam can help determine which portion of the CNS needs further investigation.
Imaging & blood tests
The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), x-ray, and/or positron emission tomography (PET scan), depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and looks for signs of metastasis. Additionally, a blood test may be taken to assess your overall health and help guide treatment decisions.
Lumbar puncture
A lumbar puncture, or spinal tap, involves inserting a needle between two vertebrae in the lower spine and extracting a sample of cerebral spinal fluid (CSF) for analysis. A local anaesthetic or sedative is given prior to the procedure. Your doctor will discuss any risks and possible complications with you prior to the procedure.
Biopsy
Once the location(s) of the cancer has been identified, the doctor will perform a biopsy to remove a section of tissue using a needle. The tissue sample will then be analysed for cancer cells. This can be done by a fine needle aspiration (FNA) or a core needle biopsy (CNB).
Prognosis (Certain factors affect the prognosis and treatment options)
While it is not possible to predict the exact course of the disease, your doctor may be able to give you a general idea based on stage, rate/depth of tumour growth, susceptibility to treatment, age, overall fitness and medical history. Generally, early-stage embryonal tumours have good prognosis and survival rates. However, if the cancer is advanced and has spread, the prognosis may not be as good and there may be a higher risk of cancer recurrence.
References
Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.