Infantile myofibromatosis, or IM, is a rare tumor that grows in the skin, muscles, bones, and sometimes in the organs of the chest or abdomen. IM tumors are benign, which means they are not cancer and do not spread to other parts of the body. But these tumors may grow large and damage nearby organs.

In the rare cases where IM runs in families, we know that changes in the genes PDGFRB and NOTCH3 are involved in causing IM. In cases where it happens randomly, we do not know what causes it. Scientists are always working to understand how cancer forms, but it can be hard to prove.

In some rare cases, IM has been found to run in families. Usually it occurs randomly.

Most babies with IM have purple-colored or skin-colored growths on their skin. But when the tumors are in the muscles or organs, symptoms may be different. Doctors usually find IM at birth when they examine the baby, but other tests may be done, too.

Imaging: If your child has symptoms of IM, your doctor will use scans such as ultrasound, MRI, or CT to see where the tumor is and how big it is.

Biopsy: To check if the tumor is IM, your doctor will do a biopsy, taking a small sample of the tumor with a needle. An expert, called a pathologist, will study cells from the sample under the microscope and run other tests to see what kind of tumor it is.

Treatment for each child will be unique. You should take your child to an expert in IM treatment to decide the best approach for their tumor. You can contact MyPART for help finding experts near you.

Treatment options to discuss with your doctor include:

Watch and wait: In some cases, the tumor grows very slowly, or even shrinks without any treatment. In this case it may be safest for your doctor to check your child’s tumor often without treating it.

Surgery: In cases where the tumor is growing in or near the organs, surgery is the main treatment to remove the tumor and prevent damage to the organs.

Chemotherapy: When surgery is not possible or does not work, chemotherapy may be used to treat IM.

The estimate of how a disease will affect your child long-term is called prognosis. Every person is different and the prognosis will depend on many factors, such as:

• Where the tumor is in the body
• How much of the tumor was taken out during surgery

If you want information on your child’s prognosis, it is important to talk to their doctor. Also, NCI has resources to help you understand cancer prognosis.

When IM does not involve the internal organs, the prognosis is very good. Many children’s tumors might even shrink over time without treatment. But, children with IM in their internal organs that are not treated have a poor prognosis. Their chance of survival is about 30%.

IM is found at birth in about 1 out of 150,000 babies. Some cases of IM may not be diagnosed or correctly diagnosed. For this reason, IM may be more common than we think. It is most common in babies and young children. Over 90% of IM cases occur in children under 2 years old.