About Childhood Cancer

Glossary of Terms

In the first days after a diagnosis, doctors and nurses often move quickly through information, and it’s easy to walk out of an appointment with a page of notes full of terms that have yet to be explained.

This glossary exists to help translate that language into something plain and steady, so you can feel a little more grounded in conversations with your child’s care team. This glossary is for general education only. It is not medical advice. If you or your family have questions about a specific diagnosis or treatment plan, please talk with your child’s medical team.

Cancer Types

Childhood cancer isn’t one disease. It is a group of many different conditions, each with its own name, behavior, and area of the body it affects. This section defines the cancers most commonly diagnosed in children, from blood cancers like leukemia to solid tumors like neuroblastoma and osteosarcoma.

Leukemia – Cancer of the blood and bone marrow, the spongy tissue inside bones where blood cells are made. It is the most common form of childhood cancer.

• acute lymphoblastic leukemia (ALL) – A type of leukemia affecting white blood cells called lymphocytes. It is the most common leukemia diagnosed in children. ALL is further classified by which type of lymphocyte is involved — B-cell ALL or T-cell ALL.
• acute myeloid leukemia (AML) – A type of leukemia affecting a different group of blood-forming cells than ALL.

Lymphoma – Cancer that begins in the lymphatic system, the network of tissues and organs that help fight infection. Includes Hodgkin and non-Hodgkin lymphoma.

Brain Tumors – An abnormal growth of cells in the brain or central nervous system. Brain and spinal cord tumors are among the most common childhood cancers.

• medulloblastoma – The most common type of malignant brain tumor in children, forming in the cerebellum.
• juvenile pilocytic astrocytoma (JPA) – A slow-growing brain tumor that develops from star-shaped support cells called astrocytes. It is one of the more common brain tumors diagnosed in children.
• atypical teratoid/rhabdoid tumor (ATRT) – A rare, fast-growing brain tumor that occurs most often in infants and very young children.

Solid Tumors – Cancers that form a mass in an organ or tissue outside the blood or lymphatic system.

• rhabdomyosarcoma – A cancer that forms in soft tissue, most often muscle, and is the most common soft-tissue sarcoma in children.
• Wilms tumor – A type of kidney cancer that primarily affects young children.
• neuroblastoma – A cancer that develops from immature nerve cells, most often found in and around the adrenal glands. It is one of the most common cancers in infants.
• Ewing sarcoma – A cancer that forms in bone or the soft tissue around bone, most often affecting the arms, legs, or pelvis.
• osteosarcoma – A cancer that begins in the cells that form bone, most often affecting the long bones of the arms and legs.
• retinoblastoma – A cancer that begins in the retina, the light-sensitive tissue at the back of the eye.

Langerhans Cell Histiocytosis (LCH) – A rare condition in which the body produces too many of a type of immune cell called Langerhans cells, which can build up and form lesions in bone, skin, or other organs. It is sometimes classified as a cancer and sometimes as a separate type of disorder, depending on the source.

Related Blood & Immune Conditions – These conditions are not cancer, but families often encounter them in the same setting, since they are commonly diagnosed and treated by pediatric hematology-oncology teams.

• aplastic anemia – A rare condition in which the bone marrow stops producing enough new blood cells. It is not a cancer, but it is often diagnosed and treated by hematology-oncology specialists.
• hemophagocytic lymphohistiocytosis (HLH) – A rare and serious condition in which the immune system becomes overactive, causing certain immune cells to attack the body’s own tissues and organs. HLH is not a cancer, but it is often treated by hematology-oncology teams.

Diagnosis & Testing

Getting to a diagnosis and monitoring a child’s health afterward involves a specific set of medical terms that families often hear for the first time all at once. These definitions explain the tests, procedures, and terminology used throughout that process.

Biopsy – A procedure in which a small sample of tissue is removed and examined to check for cancer cells.

Oncologist – A doctor who specializes in diagnosing and treating cancer. A pediatric oncologist specializes in cancers affecting children.

Pathology Report – A document describing what was found when a tissue sample was examined under a microscope.

Imaging – Tests such as X-rays, MRIs, CT scans, and ultrasounds that create pictures of the inside of the body to help identify or monitor a tumor.

Staging – The process doctors use to describe the extent of a cancer, including its size and whether it has spread.

Remission – A period during or after treatment when signs and symptoms of cancer are reduced or no longer detectable.

Relapse – The return of cancer after a period of complete remission.

Treatment Terms

Childhood cancer treatment can involve several different approaches, sometimes used in combination. The terms below explain, in general terms, what these treatments are. They are not intended to describe or recommend a course of care for any individual child.

Chemotherapy – A category of drugs used to treat cancer by targeting rapidly dividing cells.

Radiation Therapy – A treatment that uses high-energy beams to target and damage cancer cells.

Surgery – A procedure to physically remove a tumor or affected tissue.

Stem Cell Transplant – A medical procedure that replaces unhealthy or destroyed blood-forming stem cells with healthy ones. Two types are: Autologous and Allogeneic.

Bone Marrow Transplant – A specific type of stem cell transplant that requires a minor surgery for the liquid bone marrow to be extracted from the donor’s hip bones using a needle.

Immunotherapy – A category of treatment that works by helping the body’s own immune system identify and respond to cancer cells.

CAR T-Cell Therapy – A type of immunotherapy in which a patient’s own immune cells are modified in a lab to help them recognize and target cancer cells.

Proton Therapy – A type of radiation treatment that uses a beam of protons, allowing more precise targeting of a tumor while limiting exposure to surrounding healthy tissue.

Clinical Trial – A research study that tests new treatments, drug combinations, or approaches to care.

Precision Medicine – An approach to treatment that uses information about a tumor’s specific genetic makeup to help guide care decisions.

Late Effects – Health problems that can appear months or years after cancer treatment has ended.

Genetics & Research

Research into the genetic and molecular roots of childhood cancer is opening up new approaches to understanding and studying these diseases. This section covers common terms related to genetics, inherited risk, and the research process.

Cancer Predisposition Syndrome – An inherited genetic condition that increases a person’s risk of developing one or more types of cancer. Examples include Li-Fraumeni syndrome and Beckwith-Wiedemann syndrome.

Genetic Testing – Tests that look for changes in genes, chromosomes, or proteins that may be linked to inherited cancer risk.

Mutation – A change in a gene’s DNA sequence. Most childhood cancers are linked to mutations that are not inherited from a parent.

Biomarker – A biological molecule that can indicate the presence of cancer or provide information about how a tumor may behave.

Tumor Genomic Profiling – A process of analyzing the genetic makeup of a tumor to better understand it and inform research or care discussions.

Support & Care

A childhood cancer diagnosis affects the whole family, not just the patient. These terms cover the programs, services, and phases of care designed to support patients, siblings, and families throughout and after treatment.

Survivorship – A term used to describe the different phases of life following a cancer diagnosis. It’s often broken down into three stages, each with a different focus and set of needs.

• Active Treatment – The period from diagnosis through the end of active treatment, when a child is receiving therapies such as chemotherapy, radiation, or surgery, along with frequent monitoring from their care team.
• Off-Therapy – The period immediately after active treatment ends. A child transitions away from regular treatment visits, but continues to be closely monitored as their body adjusts and their care team watches for any changes.
• Long-Term Survivorship – The ongoing phase of life, often years beyond the end of treatment, focused on monitoring for late effects and supporting a survivor’s long-term health and well-being.

Palliative Care – Specialized medical care focused on providing relief from symptoms and stress of a serious illness, which can be provided alongside other treatment.

Psychosocial Support – Services that address the emotional, social, and mental health needs of a patient and their family.

Survivorship Care Plan – A summary of a patient’s cancer treatment history and recommended follow-up care, used to guide long-term monitoring.

Sibling Support – Programs and resources designed specifically to help brothers and sisters of a child with cancer cope with the experience.