Primary bone cancers start in the bones, and are distinguished from metastatic bone cancer, which is a cancer that has started elsewhere but spread into the bone. Primary bone cancers make up about 3% of childhood cancer; the most common types of bone cancer in children are osteosarcoma and Ewing sarcoma.

Brain tumors are around 26% of all childhood cancers. There are a variety of different types of brain tumors, classified by where the tumor started. Treatment and prognosis depends heavily on the exact type and location of the tumor.

Hepatoblastoma is the most common liver cancer of children and accounts for about 1% of all childhood malignancies. It is most commonly diagnosed in children under the age of three and virtually all patients with hepatoblastoma are less than five.

Leukemias involve cancers of the bone marrow and blood. They make up about 30% of all childhood cancers. The two types are acute lymphocytic leukemia (ALL) and acute myelogenous leukemia (AML), both of which can grow quickly and require immediate treatment.

Lymphoma begins in the immune system, and is likely to be found the lymph nodes, tonsils, thymus, or spleen. Hodgkin lymphoma accounts for around 3% of childhood cancer and is most common in young adults; non-Hodgkin lymphoma accounts for around 5% of childhood cancers and occurs in younger children (but is rare in children under 3). Lymphoma is generally a rapidly-growing form of cancer and requires immediate treatment.

Medulloblastoma is the most common malignant brain tumor in children. It originates in the back part of the brain called the cerebellum. In up to 1/3 of cases, it can spread to other parts of the brain and spinal cord. Most cases are diagnosed before age 10.

Neuroblastoma is a type of childhood cancer that develops in nerve tissue outside of the central nervous system. Although neuroblastoma can start anywhere, it is most commonly found in the abdomen. It primarily affects infants and very young children and constitutes about 6% of childhood cancers.

Retinoblastoma is a rare form of cancer that rapidly develops from the immature cells of a retina. It is the most common primary malignant intraocular cancer in children. This cancer is most common in children under the age of two (it is rarely found in children older than 6). It constitutes about 2% of childhood cancers.

Atypical teratoid/rhabdoid tumors (AT/RT)
A rhabdoid tumor is a rare, highly aggressive tumor found in the cerebellum. These tumors are believed to represent a distinct entity and believed to be a subset of medulloblastomas. On Average, these tumors occur in young children, around 3.5 years old at diagnosis.

Soft tissue sarcomas in children can appear in muscle, fat, fibrous tissue, blood vessels, tendons, connective tissues, or other supporting tissues of the body. Rhabdomyosarcoma accounts for about half of the cases of pediatric soft tissue sarcomas. Less frequent pediatric soft tissue sarcomas include fibrosarcoma, mesenchymoma, synovial sarcoma, and liposarcoma.

A spinal cord tumor is a growth of abnormal cells within the spinal cord. A tumor forms as cells grow and/or replicate too quickly, or do not die at the correct time. The tumor may be either malignant (cancerous) or benign (non-cancerous). Both benign and malignant tumors can cause similar types of symptoms.

Wilms tumor is a cancer of the kidney. It is one of the most common types of childhood cancer, with approximately 500 new patients a year in the USA alone. There are several other less common types of kidney cancer that affect children and teenagers. These include clear cell sarcoma, malignant rhabdoid tumor, and renal cell carcinoma.