Osteochondroma (Exostosis)

Osteochondroma is the most common type of non-cancerous (benign) bone tumor. An osteochondroma is a hard mass of cartilage and bone that generally appears near the growth plate (a layer of cartilage at the ends of a child’s long bones). The majority of children with an osteochondroma only have a single tumor. Less commonly, osteochondromas will occur as multiple tumors.

Although osteochondromas do not spread beyond the affected bone, they may grow in size as your child grows. An osteochondroma ordinarily stops growing when a child reaches full height (around age 14 in girls and 16 in boys).

In most cases, osteochondromas don’t create problems and treatment isn’t needed. Surgery is only necessary if the tumor is causing significant pain, putting pressure on blood vessels or nerves, or very large in size.

Can an osteochondroma become cancerous (malignant)?

Very rarely, an osteochondroma can transform into a malignant condition later in adulthood. Your child’s doctor will probably want to keep an eye on the condition for this reason. It is extremely unusual and is therefore not a reason to remove all osteochondromas.

What causes osteochondroma in children?

The cause of osteochondroma is unknown, but the tumor is thought to be related to an abnormality in the growth plate, causing a bony prominence to grow away from the bone.

If a child has several osteochondromas, they are usually the result of a genetic disorder known as multiple hereditary exostoses (MHE) or multiple osteochondromas. However, there is also a non-heredity form of MHE in which multiple osteochondromas occur by chance (sporadically).

What are the symptoms of osteochondroma in children?

In general, osteochondromas are hard masses that grow on top of the bone and only cause pain when nerves, muscles, or tendons rub against them.

Keep in mind that each child can experience symptoms of osteochondroma differently, depending on the size and location of the tumor or tumors.

Because the symptoms may also be caused by other, more serious health conditions, it is important to be evaluated by a physician to get an accurate diagnosis. Always consult your child's physician if you have concerns.

The following are the most common symptoms of osteochondromas:

  • a hard, painless mass; the mass can be painful if nearby muscles or tissues rub over the osteochondroma and become inflamed 
  • different limb lengths
  • shorter than average height for age
  • joint and muscle pains

How Boston Children’s Hospital Boston approaches osteochondroma

Experts in the Bone and Soft Tissue Tumors Program at Boston Children’s are devoted to caring for children and teenagers with osteochondromas and other bone and soft tissue disorders.

Our multidisciplinary approach to care ensures that your child’s case receives careful consideration from experts in several fields before your care team develops a personalized treatment plan.

Osteochondroma Reviewed by Megan E. Anderson, MD
© Boston Children’s Hospital 2019