Inflammatory myofibroblastic tumor, or IMT, forms in tissues called mucosal surfaces and mesentery. Mucosal surfaces are found in your eyes, nose, mouth, digestive tract, lungs, and genital and urinary tracts. Mesentery connects the organs in your abdomen. IMT usually starts in the lungs but may begin in the bladder, uterus, larynx, stomach, liver, or intestine. IMT may also be called inflammatory fibrosarcoma or IMFT.

IMT is named for two types of cells in the tumor. IMT forms from a type of cell called a myofibroblast. Myofibroblasts help keep the shape of organs and heal wounds. IMTs also contain a lot of immune cells, making the tumor look “inflamed” like an infection.

IMT is usually benign, meaning that it is not cancer and these tumor cells usually do not travel to other parts the body. However, IMT can invade nearby tissue and cause a lot of problems. IMT can grow in the way of important organs such as the lung or stomach. In very rare cases, IMT can spread to distant organs.

IMTs are mostly found in children and young adults but can occur at any age.

The underlying cause of inflammatory myofibroblastic tumors (IMTs) remains unknown. While some researchers believe it is a true neoplasm, others believe that it represents an immunologic response to an infectious or noninfectious agent. Several associations have been reported between IMT and infections, including:

• organizing pneumonia
• Mycobacterium avium intracellulare
• Corynebacterium equi (a bacteria that affects the lungs)
• Campylobacter jejuni (a common cause of gastroenteritis)
• Bacillus sphaericus
• Coxiella burnetii
• Epstein-Barr virus
• E. coli
• occlusive phlebitis of intrahepatic veins

Associations have also been reported between IMT and:

• previous abdominal surgery
• trauma
• ventriculoperitoneal shunt
• radiation therapy
• steroid usage

An inflammatory reaction to an underlying, low-grade malignancy has also been proposed as a cause. Because there is limited information available to support or refute any of these, the mechanism behind the development of IMTs is still unclear.

IMT is very rare and occurs in less than one in one million people. An estimated 150-200 people are diagnosed in the US annually.

Although IMT can cause specific symptoms, some people with IMT do not have any. IMT symptoms depend on where the tumor is and its size. Symptoms may include fever, night sweats, weight loss, generally not feeling well, and pain at the site of the tumor.

Imaging: If you have symptoms of IMT, your doctor will use imaging scans such as CT, ultrasound, or MRI to determine where the tumor is in the body and its size.

Biopsy: To check if the tumor is IMT, your doctor will perform a biopsy, taking a small sample from the tumor with a needle. A pathologist will study the cells from the sample under the microscope to see what kind of tumor it is.

Molecular Diagnostics: Molecular diagnostics are techniques used to identify a disease by studying molecules, such as proteins, DNA, and RNA, in a tissue or fluid. They are used because IMTs can look like other tumors or infections, and can be hard to diagnose. Your doctor will test your biopsy sample for markers that show whether it is IMT. This helps them decide which treatment is best for you.

Treatment of IMT depends on where the tumor is located, which proteins it makes, and whether it has spread to other parts of the body.

Surgery: IMTs are hard to completely remove by surgery and often come back. It is important to follow up with your doctor to check if the tumor has returned.

Chemotherapy: If the IMT is faster growing or has returned after surgery, your doctor may use chemotherapy to treat it.

Targeted Therapy: Some IMTs make proteins that can be targeted by new drugs. Depending on how well your IMT is removed by surgery, your doctor may try one of these targeted therapies.

IMT is not known to run in families.

Scientists are always working to understand how tumors form, but it can be hard to prove. We know that in some cases of IMT, chromosomes (the parts of your cells that contain all of your genes) break apart and get put back together in the wrong way. This can cause cells to not function like they should. In IMT, a gene called ALK can join with other genes. Your doctor may look for this change in chromosomes to confirm that your tumor is IMT.

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

• Where the tumor is in your body
• If the tumor has spread to other parts of your body
• How much of the tumor was taken out during surgery

If you want information on your prognosis, it is important to talk to your doctor. NCI also has resources to help you understand cancer prognosis.

Doctors estimate IMT survival rates by how groups of people with IMT have done in the past. Given that there are so few IMT patients, these survival rates may not be very accurate. They also don’t consider newer treatments being developed. In general, those with IMT that is completely removed by surgery do very well and most people survive past 10 years.