Rhabdomyosarcomas (RMSs) are a rare form of sarcoma (cancer arising from bone, connective tissue and soft tissue) that develops in muscles. It is the most common soft tissue sarcoma in children and adolescents.

There are two kinds of muscle cells: smooth muscle cells and skeletal muscle cells. Smooth muscle cells are responsible for involuntary movement, and are found within organs, glands and blood vessels. They aid in food digestion, pumping blood throughout the body, urine flow and pregnancy contractions. Cancer that originates from smooth muscles is called leiomyosarcoma. In contrast, skeletal muscle cells are responsible for voluntary movement, and are attached to the bones in the body. They enable movement by contracting and relaxing in response to voluntary messages sent by the brain. Cancer that originates in skeletal muscle cells is called rhabdomyosarcoma (RMS).

RMS is slightly more common in males, and is often diagnosed in children under 10 years old. However, this disease can develop in anyone.

Types of Rhabdomyosarcoma

There are four main types of RMS, which are classified by how the cancer cells look under the microscope.

Embryonal Rhabdomyosarcoma (ERMS)

Embryonal RMS (ERMS) is the most common subtype of rhabdomyosarcoma, and generally affects children under five years of age. It is most commonly found in the head, neck or genitourinary organs, but can occur anywhere in the body. There are two common subtypes of EMRS. 

Botryoid Embryonal Rhabdomyosarcoma

Botryoid (meaning a bunch of grapes) EMRS is a rare type of tumour that is named for their distinctive grape-like appearance. It is most commonly found in the walls of the vagina or bladder in female infants and young girls. While this subtype can be aggressive, the prognosis can be good when caught early. 

Spindle-Cell Embryonal Rhabdomyosarcoma

Spindle-cell EMRS is a rare type of tumour that is named for their spindle (long and slender) appearance. It is most commonly found in the paratesticular region (area around the testis and spermatic cord) of males under the age of one. This subtype is generally considered less aggressive, and can have a good prognosis.

Alveolar Rhabdomyosarcoma (ARMS)

Alveolar rhabdomyosarcoma (ARMS) is a less common type of rhabdomyosarcoma that generally affects kids over five years old and teenagers. This type of tumour is named for their clustered appearance, much like alveoli in the lungs. It is most commonly found in the muscles of the arms, legs, chest or abdomen. ARMS can be aggressive, and may not have as good of a prognosis as ERMS. 

Anaplastic Rhabdomyosarcoma

Anaplastic rhabdomyosarcoma, also known as pleomorphic rhabdomyosarcoma, is the least common subtype of this disease. Anaplastic is a term given to cancer cells that divide rapidly, and have little to no resemblance of normal cells. It is mainly found in adults, and is considered very rare in children. Anaplastic rhabdomyosarcoma is often considered aggressive, but can have a good prognosis when caught early.

Treatment

If a rhabdomyosarcoma is detected, it will be staged and graded based on size, metastasis (whether the cancer has spread to other parts of the body) and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you. 

Cancers can be staged using the TNM staging system: 

• T (tumour) indicates the size and depth of the tumour. 
• N (nodes) indicates whether the cancer has spread to nearby lymph nodes. 
• M (metastasis) indicates whether the cancer has spread to other parts of the body. 

This system can also be used in combination with a numerical value, from stage 0-IV: 

• Stage 0: this stage describes cancer cells in the place of origin (or ‘in situ’) that have not spread to nearby tissue. 
• Stage I: cancer cells have begun to spread to nearby tissue. It is not deeply embedded into nearby tissue and had not spread to lymph nodes. This stage is also known as early-stage cancer.
• Stage II: cancer cells have grown deeper into nearby tissue. Lymph nodes may or may not be affected. This is also known as localised cancer. 
• Stage III: the cancer has become larger and has grown deeper into nearby tissue. Lymph nodes are generally affected at this stage. This is also known as localised cancer. 
• Stage IV: the cancer has spread to other tissues and organs in the body. This is also known as advanced or metastatic cancer.

Cancers can also be graded based on the rate of growth and how likely they are to spread: 

• Grade I: cancer cells present as slightly abnormal and are usually slow growing. This is also known as a low-grade tumour. 
• Grade II: cancer cells present as abnormal and grow faster than grade-I tumours. This is also known as an intermediate-grade tumour.  
• Grade III: cancer cells present as very abnormal and grow quickly. This is also known as a high-grade tumour.  

Once your tumour has been staged and graded, your doctor may recommend genetic testing, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.  

Treatment is dependent on several factors, including age, subtype, location and stage of disease.

Treatment options for rhabdomyosarcomas may include:

• Surgery, potentially including a wide local excision (removal of the tumour and a healthy margin of tissue around it). 
• Chemotherapy.
• Radiation therapy.
• Immunotherapy.
• Targeted therapy.
• Clinical trials.
• Palliative care.

For more information on the treatment options, please refer to the Rare Cancers Australia Treatment Options page.

Risk factors

While the cause of rhabdomyosarcoma remains unknown, the following factors may increase your risk of developing the disease:

• Certain genetic conditions, such as:
  • Li-Fraumeni syndrome.
  • Beckwith-Wiedemann syndrome.
  • Neurofibromatosis type 1 (NF1).
  • Costello syndrome.
  • Noonan syndrome.
• Having a family history of cancer.

Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.

Early symptoms

As rhabdomyosarcoma can develop anywhere in the body, the symptoms will vary based on the location of the tumour. 

Head and Neck Rhabdomyosarcomas

Symptoms of a rhabdomyosarcoma in the head and neck region may include:

• Headache.
• Bulging and/or swelling of the eyes.
• Unusual bleeding in the nose, throat and/or ears. 
• A lump in the affected region.
• Pain and/or redness in the affected area.
• Earache.
• Sinus congestion.
• Unexplained weight loss.
• Fatigue.

Urinary and Reproductive Systems Rhabdomyosarcomas

Symptoms of a rhabdomyosarcoma in the urinary and reproductive system may include:

• Difficulties urinating.
• Blood in the urine.
• Difficulties with bowel movements.
• Unusual bleeding from the vagina and/or rectum. 
• Pain and/or redness in the affected area.
• A lump in the affected region.
• Unexplained weight loss.
• Fatigue.

Abdominal and Pelvic Rhabdomyosarcomas

Symptoms of a rhabdomyosarcoma in the abdomen or pelvis may include:

• Vomiting.
• Abdominal pain.
• Yellowing of skin and/or eyes (jaundice) – only in tumours of the bile ducts.
• Unexplained weight loss.
• Fatigue.
• Lump in the affected region. 
• Bone pain.

Rhabdomyosarcomas of the Back, Arms and Legs

Symptoms of a rhabdomyosarcoma in the back, arms and legs may include:

• Swelling in the affected area.
• Lump in the affected area.
• Bone pain.
• Fatigue.
• Unexplained weight loss. 

Not everyone with the symptoms above will have cancer but see your general practitioner (GP) if you are concerned.

Diagnosis/diagnosing

If your doctor suspects you have a rhabdomyosarcoma, they may order the following tests to confirm the diagnosis and refer you to a specialist for treatment. 

Physical examination 

Your doctor will collect your overall medical history, as well as your current symptoms. Following this, they may examine your body to check for any abnormalities. 

Imaging & blood tests 

The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), x-rays, bone scan and/or positron emission tomography (PET scan), depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and looks for signs of metastasis. Additionally, a blood test may be taken to assess your overall health and help guide treatment decisions. 

Lumbar puncture

A lumbar puncture, or spinal tap, involves inserting a needle between two vertebrae in the lower spine and extracting a sample of cerebral spinal fluid (CSF) for analysis. A local anaesthetic or sedative is given prior to the procedure. Your doctor will discuss any risks and possible complications with you prior to the procedure. 

Bone Marrow Aspiration & Biopsy

Once the location of the cancer has been identified, the doctor will perform a biopsy to remove a section of tissue using a needle. In most cases, this will be done by a bone marrow aspiration and biopsy. This process involves inserting the needle into the hipbone (or breastbone in some cases) to remove samples of solid and liquid bone marrow. These samples will then be analysed for cancer cells.

Prognosis (Certain factors affect the prognosis and treatment options)

While it is not possible to predict the exact course of the disease, your doctor may be able to give you a general idea based on stage, rate/depth of tumour growth, susceptibility to treatment, age, overall fitness and medical history. Generally, early-stage rhabdomyosarcomas have a good prognosis and survival rates. However, if the cancer is advanced and has spread, the prognosis may not be as good and there may be a higher risk of cancer recurrence.  

References

• American Cancer Society
• Mayo Clinic
• National Cancer Institute
• UpToDate

^{Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.}