Rhabdomyosarcoma (RMS or ‘rhabdo’) is a tumor made up of cancerous cells that look like immature muscle cells. In the United States, about 350 new cases are diagnosed each year in children less than 15 years old. Almost two-thirds of children’s rhabdo cases develop in children under 10.

RMS can arise in any part of the body, but the most common sites are:

• Adjacent to the base of the skull (parameningeal)
• Around the eye (orbital)
• Sites in the head and neck, such as the cheek or lip
• Arms and legs (extremities)
• Urinary system and reproductive sexual organs (genitourinary system which includes bladder, vagina, prostate and areas around the testicles)

In children, there are two major subtypes of RMS, based on the way the tumor cells look under the microscope.

Embryonal rhabdomyosarcoma (ERMS) is the most common type.

• ERMS tends to occur in younger children. Common sites include the eye, known as the orbit, the head and neck, and the genitourinary system.
• ERMS often occurs in hollow organs that are lined with mucosa (moist tissue), such as the nasal passages, vagina and bladder, and can appear as a botryoid (grape-like) mass on the surface. Tumors having this botryoid histology are a subtype of embryonal RMS.

Alveolar rhabdomyosarcoma (ARMS) makes up about 25-40% of RMS. This type is more commonly found in adolescents and often occurs on the arms and legs.

Symptoms of Rhabdomyosarcoma

Most often rhabdomyosarcoma presents as a mass; however, the signs and symptoms depend on the location of the primary tumor.

• Genitourinary tumors may present as in blood in the urine, difficulty urinating or bleeding from the vagina. They can also cause a mass in the vagina or next to the testicle in the scrotum.
• Parameningeal tumors may cause facial asymmetry, double vision, difficulty breathing through or drainage from one nostril, ear discharge, headaches or facial pain. Swelling around the eye is common with tumors of the orbit.
• Extremity tumors often present as a rapidly enlarging, firm lesion.

Diagnosing Rhabdomyosarcoma

Many tests and procedures are performed to determine if and where cancer cells are present in the body. The exact combination of tests needed to diagnosis a child depends on the symptoms that are present and the type of cancer suspected. It is important to identify the extent of disease for children with a suspected cancer. This is accomplished in the following manner:

• Examination of the site of the tumor: The tumor site can be examined by several imaging studies, such as an MRI, to determine the size, exact location and if it has invaded any areas in surrounding body structures.
• Biopsy: The only way to determine the type of tumor is to obtain a piece of it for examination by a pathologist. This is known as a biopsy. In some cases, the primary tumor can be completely removed at the same time.
• Examination of the body for signs the tumor has spread: The common sites of metastasis (spread of the cancer cells) include the lungs, bone marrow and bones. Some of the common tests that may be used in evaluation include:
• CT scan of the lungs
• Bone scan
• Bone marrow aspirate
• Bone marrow biopsy
• PET scans are sometimes used to look for metastatic sites

Under the microscope, rhabdomyosarcoma can look similar to several other types of children’s cancers such as neuroblastoma, Ewing sarcoma and lymphoma. It is important to be sure about the type of cancer and its location before deciding on a treatment plan.

Survival

It is now possible to cure nearly 3 of every 4 children with rhabdomyosarcoma. Prognostic factors are characteristics of the patients and their tumors that are designated as more or less “favorable” based on the outcome of thousands of patients treated over decades. These factors are also used to determine the best choice of therapy. Although the “unfavorable” forms of cancer require more intensive treatment than “favorable,” all RMS are treated with chemotherapy.  Surgery is always used to make a diagnosis and sometimes as part of the treatment. In most cases, radiation therapy is part of the treatment.

The most important prognostic factors include:

• Extent of the disease: This is defined by the Intergroup Rhabdomyosarcoma Study (IRS) Stage and Group systems.
• Primary tumor site: Some tumor sites are defined as favorable. These include tumors that begin in the orbit, superficial sites in the head and neck, the vagina and around the testicles. All other sites, including parameningeal tumors, extremity, and bladder genitourinary sites, are classified as unfavorable.
• Histology subtype: Embryonal histology tumors have a more favorable outcome.
• Age: Patients under one and over 10 years of age have a somewhat less favorable prognosis.
• Presence of distant metastasis: Patients whose tumors have metastasized (spread to other areas) at the time of diagnosis have a less favorable prognosis.

Causes of Rhabdomyosarcoma

Researchers currently DO NOT know what causes rhabdomyosarcoma. In most cases, there are no clear predisposing risk factors for the development of RMS. However, it has been associated with other conditions, including:

• Neurofibromatosis type 1
• Beckwith-Wiedemann syndrome
• Li-Fraumeni syndrome
• Cardio-facio-cutaneous syndrome
• Costello syndrome

Children with these conditions are at higher risk for rhabdomyosarcoma, but these account for only a small fraction of cases. These syndromes usually require medical care, so you would know if your child had one of them.

Last updated July, 2011

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