Why does childhood cancer cause new lump or swelling?

A cancerous growth can collect in one area and be felt or seen as a lump. Some childhood cancers affect blood-forming or immune tissues, which can enlarge lymph nodes or organs. Swelling may also occur when a mass presses on nearby structures or changes the flow of fluid. The location can vary, including the neck, chest, abdomen, pelvis, or a limb.

Many childhood lumps are caused by non-cancer conditions such as infection, injury, a cyst, or normal tissue. Features such as how quickly it appeared, whether it is painful, whether it changes, and whether the child has fever, tiredness, weight change, bruising, or reduced appetite help guide assessment. A lump cannot be identified by appearance alone.

Arrange a medical assessment for a new lump or swelling that persists, grows, feels firm or fixed, returns, or comes with other changes. Note when it was first noticed, its location, whether it is tender, and whether the child’s movement, breathing, eating, or sleep has changed. Avoid repeatedly pressing it, and do not apply heat or medicine without clinical advice.

Seek prompt medical advice for a growing lump, unexplained bruising, ongoing fever, marked tiredness, night sweating, or reduced appetite. Seek urgent help for trouble breathing or swallowing, severe pain, sudden weakness, fainting, or swelling that develops rapidly.

What could be causing this lump or swelling? What changes should we monitor at home? Does the location or growth pattern call for imaging or another assessment? Which symptoms should lead us to seek urgent help?