Rhabdomyosarcoma (RMS)

A rhabdomyosarcoma (RMS) is a type of soft tissue sarcoma, a malignant (cancerous) tumor made up of muscle cells.

RMS is the most common soft tissue cancer in children and teens. But they are still rare—only about 350 cases are diagnosed each year in the U.S. In adults, rhabdomyosarcoma represents less than 1 percent of the 13,000 soft tissue sarcomas found annually.

Although the subtypes can form anywhere in the body, the most common type of rhabdomyosarcoma (embryonal) is most often found in the head and neck. Other locations include the genitals, urinary system, arms and legs, and chest, abdomen (belly), pelvis, and back. At times, it can also form as an unusual brain tumor or kidney cancer.

Rhabdomyosarcoma tumors can grow quickly and reach a large size—up to 5 centimeters across. Some tumors may continue to grow even with treatment, and they may return after treatment. RMS may also metastasize (spread), most often to the lungs, lymph nodes, bones, or bone marrow.

Rhabdomyosarcoma is a challenging cancer to treat. The best care comes when a team of specialists work together. The Sarcoma Program at Penn Medicine’s Abramson Cancer Center has one of the nation’s most experienced teams, highly skilled in treating rhabdomyosarcoma. Our specialists work closely with the Sarcoma Program at the Children’s Hospital of Philadelphia.

There are four types of rhabdomyosarcoma categorized based on where they occur, how they act, and who they affect:

• Embryonal rhabdomyosarcoma: This is the most common type of rhabdomyosarcoma, accounting for about 60 percent of cases. It mainly affects children and younger teens, most frequently forming in the head and neck, genitals, and urinary tract. These tumors generally respond well to treatment.
• Alveolar rhabdomyosarcoma: Accounting for about 20 percent of cases, this type of rhabdomyosarcoma is often more aggressive. It mainly affects teens and forms in the arms, legs, chest, belly, genitals, or anus.
• Spindle cell/sclerosing rhabdomyosarcoma: These rhabdomyosarcomas are further broken into subtypes. One subtype forms in male genitals. Another forms in the chest, belly, pelvis, and back, mainly in infants. A third forms in the head and neck, affecting children, teens, and adults and often acting more aggressively.
• Pleomorphic rhabdomyosarcoma: This type mainly affects adults and forms in the arms and legs. It’s an aggressive form of RMS.

Rhabdomyosarcomas may not cause any symptoms at first. In the head neck, tumors usually start as a painless lump. As a tumor grows, you may notice signs as it pushes on other tissues. These symptoms depend on where the tumor has formed and may include:

• Blood in the urine or from the nose, throat, vagina, or rectum
• Bulging eye or crossed eyes
• Harder time emptying bladder or bowels
• Headache
• Joint stiffness
• Pain or discomfort in the affected area
• Reddening of the skin
• Swelling

The exact causes of rhabdomyosarcoma are unknown. However, some genetic syndromes raise the risk of developing the disease. These changes are often inherited from parents, but may also develop on their own in the womb.

One of the genetic syndromes that raises the risk of developing RMS is called neurofibromatosis type 1 (NF1). This syndrome raises the risk for developing tumors in protective covers for certain nerves, including malignant peripheral nerve sheath tumors (MPNST).

Another genetic condition called Li–Fraumeni syndrome (LFS) can also lead to rhabdomyosarcoma as well as other sarcoma types.

Other rare genetic syndromes raise the risk only for embryonal rhabdomyosarcoma. These syndromes, many of which have ties to shorter stature, include:

• Beckwith-Wiedemann syndrome
• Bloom syndrome
• Constitutional mismatch repair syndrome
• Costello syndrome
• DICER1 syndrome
• Gorlin syndrome (nevoid basal cell carcinoma syndrome)
• Nijmegen breakage syndrome
• Noonan syndrome
• Rubinstein-Taybi syndrome
• Werner syndrome

If our team suspects rhabdomyosarcoma, we will perform a physical exam and discuss any symptoms you’ve noticed. Imaging tests will provide more information on the tumor’s size and location. The scans can also show whether any cancer has spread. Depending on where the tumor is located, we may choose computed tomography (CT) or magnetic resonance imaging (MRI).

To confirm a rhabdomyosarcoma diagnosis, we will also recommend an image-guided needle biopsy. This procedure removes a small sample of the tumor for analysis by a specialized pathologist with expertise in diagnosing sarcomas. The pathologist looks at the tumor cells under a microscope and performs lab testing to determine whether it is RMS.

If we suspect an undiagnosed genetic syndrome, we can also offer genetic testing.

The information from the exam, scans, and biopsy help us stage the sarcoma and create the most effective treatment plan for you.

Our treatment recommendations for rhabdomyosarcoma take into account the tumor’s location and how aggressive it is. We also consider the side effects of treatment and how they might impact appearance and body function. This is especially true for treatment of children and teens.

To preserve appearance and function, we may not recommend surgery for tumors in some areas of the head and neck, hands, feet, or brain. Instead, we may treat these tumors with chemotherapy and radiation therapy.

For tumors in other locations, surgery may be the best option. Sarcoma surgery is usually most successful when the tumor is removed in one piece—an approach we specialize in. We may prescribe chemotherapy before surgery to shrink the tumor and make it easier to remove, and after surgery to try to stop cancer from returning. Many people with rhabdomyosarcoma also have radiation therapy before surgery to reduce the chance that cancer returns.

For RMS that returns or spreads, treatment options include chemotherapy, radiation therapy, or more surgery. Researchers are also exploring new options in sarcoma clinical trials. These treatments may include immunotherapy, in which the immune system fights cancer, as well as targeted therapy to stop the pathways cancer cells use to grow.