Medulloblastoma

Sometimes, a sick spot grows in a child's brain.

This spot is at the back and bottom of the brain. It can grow very fast. It can move through the fluid in the brain. This can spread the spot to the spine.

A sick child might feel very tired. They may have a headache or feel sick to their stomach. They might also stumble when they walk.

Doctors try to take the spot out with surgery. They may also use special medicine or light to help. These treatments help many children get well.

We hope all children stay healthy and strong.

Medulloblastoma is a type of brain cancer. It mostly affects children. This tumor grows in the cerebellum. The cerebellum is a small part at the back and bottom of the brain. It helps with balance and movement.

These tumors grow very fast. They can spread through the fluid in the brain. This can cause the cancer to move to the spinal cord. Scientists call this spread "drop metastasis."

Children may feel tired or have a headache. They might also feel sick to their stomach. Some children may stumble when they walk.

Doctors use many ways to treat this. They often start with surgery to remove the tumor. They may also use chemotherapy. This is a type of strong medicine. They might also use radiation. Radiation uses light to kill sick cells.

There are four main types of this cancer. We call these subgroups. One type is called WNT. Children with the WNT type often do very well. Another type is called Sonic Hedgehog. Doctors study these groups to find the best care.

Medulloblastoma is a type of brain cancer that mostly affects children. It starts in the cerebellum, which is a small part at the bottom and back of the brain. This area sits in a space called the posterior fossa. The brain has two main parts: a large top part called the cerebrum and the smaller cerebellum below it. A thin membrane called the tentorium separates these two areas. Because these tumors grow below that membrane, doctors call them infratentorial. This cancer is very serious because it grows quickly and can spread. It moves through the cerebrospinal fluid to other parts of the brain or the spinal cord. When it travels all the way down to the base of the spine, doctors call it "drop metastasis."

This cancer works by growing from cells that did not develop quite right. These are often called immature or embryonal cells. In the cerebellum, certain stem cells may stop dividing or changing into normal cells. Instead, they grow into a tumor. Scientists have found that there are actually four different molecular subgroups of this cancer. These are named WNT, Sonic Hedgehog (or SHH), Group 3, and Group 4. Each group comes from a different starting point in the brain. For example, WNT tumors start in the lower rhombic lip of the brainstem. SHH tumors start in a layer called the external granular layer.

Doctors have learned a lot about these groups through many years of study. In the past, they grouped these tumors by how they looked under a microscope. Now, they use genomic studies to look at the tiny instructions inside the cells. This helps them see that the four subgroups are actually very different. For instance, WNT patients often have an excellent prognosis, which means they are likely to recover well. However, patients in Group 3 often have a poor prognosis. Some studies, like the HIT-SIOP PNET 4 study, looked at 340 children across Europe. That study found that the five-year survival rate was between 85% and 87% for standard-risk patients.

Finding the right way to treat the tumor is a very important job. Doctors usually start by trying to remove as much of the tumor as possible through surgery. They may also use chemotherapy, which is a strong medicine. They might also use radiation to help kill the sick cells. Some doctors use proton beam irradiation to try and protect the heart and hearing. For children under four years old, chemotherapy might even delay the need for radiation. However, these treatments can have hard side effects. They can sometimes cause problems with growing, hearing, or how the brain works.

Understanding these facts helps doctors provide better care for every child. Even though the cancer is hard to fight, new tools are being tested. Scientists are looking at things like "liquid biopsies" to monitor the tumor. They are also studying how certain genes, like MYC or PTCH1, change how the cancer acts. In some studies, adding a medicine called carboplatin helped more children survive. We can compare these different subgroups to different types of weather. Just as a storm might be light or heavy, these subgroups tell doctors how strong the cancer might be. This knowledge helps them choose the best path for healing.

Medulloblastoma is a common type of primary brain cancer that affects children. It originates in the cerebellum, which is located at the back and bottom of the brain. This area sits within the posterior fossa, a space at the floor of the skull. The brain is divided into two main parts by a membrane called the tentorium. The larger cerebrum sits on top of this membrane. The smaller cerebellum sits below it. Because these tumors grow in the region below the tentorium, they are called infratentorial tumors.

This cancer is characterized by being invasive and growing very rapidly. Unlike many other brain tumors, medulloblastomas spread through the cerebrospinal fluid. This fluid flows around the brain and down the spinal cord. Because of this, the cancer frequently metastasizes to different surfaces of the central nervous system. When the cancer spreads all the way down to the cauda equina at the base of the spinal cord, it is called "drop metastasis." This ability to travel through the fluid makes the disease difficult to manage.

Scientists believe these tumors arise from cerebellar stem cells. These are cells that were prevented from dividing or differentiating into normal cell types. The specific cell of origin depends on the molecular subgroup of the tumor. For example, WNT tumors originate from the lower rhombic lip of the brainstem. SHH tumors originate from the external granular layer. In the past, doctors classified these tumors using histology, which is the study of tissue under a microscope. Now, integrated genomic studies show that medulloblastoma is composed of four distinct molecular variants.

These four molecular subgroups are WNT/β-catenin, Sonic Hedgehog (SHH), Group 3, and Group 4. Each group has different clinical characteristics and outcomes. The WNT subgroup has an excellent prognosis, meaning patients often recover well. The SHH subgroup is the best characterized, with 25% of human tumors having mutations in genes like Patched, Sufu, or Smoothened. Group 3 patients generally have a poor prognosis. Group 4 is considered to have an intermediate prognosis.

Diagnosis often involves using T1- and T2-weighted MRI scans. These scans show the tumor as having heterogeneous enhancement near the fourth ventricle. Under a microscope, the tumor appears solid and pink-gray in color. It is very cellular and shows high mitotic activity, which means the cells are dividing quickly. Doctors may also use DNA methylation profiling to help classify the specific subgroup. This helps them predict how the disease will behave. The Chang staging system is also used during the diagnostic process.

Treatment usually begins with maximal surgical removal of the tumor. Doctors may then add radiation to the entire neuraxis, which includes the brain and spinal cord. Chemotherapy is also a common part of the treatment plan. Using a combination of surgery, radiation, and chemotherapy can increase disease-free survival. In some cases, this combination allows for a 5-year survival rate of more than 80%. Some evidence suggests that proton beam irradiation may reduce damage to the heart or hearing. However, these treatments can cause long-term side effects like cognitive impairment or endocrine disruption.

Statistics show that medulloblastoma affects just under two people per million every year. It affects children ten times more often than adults. It is the most common malignant brain tumor in children, making up 14.5% of new pediatric brain tumor diagnoses. Historically, the cumulative relative survival rate was 60% at five years. It dropped to 52% at ten years and 47% at twenty years. However, children often do better than adults. In the HIT-SIOP PNET 4 study, standard-risk children had a 5-year survival rate between 85% and 87%.

Researchers use various models to study this cancer and find new treatments. Scientists have used rat models to identify genes like p53 that are involved in cancer. They have also used mouse models to study the SHH type of medulloblastoma. In these mice, the down regulation of a protein called Cxcl3 caused frequent tumors. Interestingly, treating these mice with Cxcl3 prevented the growth of the lesions. This makes Cxcl3 a potential target for future human therapies. Modern research is also exploring liquid biopsies to monitor how a patient responds to treatment.