An Overview of Rhabdomyosarcoma

Rhabdomyosarcoma is a rare skeletal muscle cancer that occurs most often in childhood. It's a type of sarcoma. Sarcomas are tumors that arise from mesothelial cells, the cells in the body which give rise to connective tissue such as bone, cartilage, muscle, ligaments, other soft tissues. Roughly 85% of cancers, in contrast, are carcinomas, which arise from epithelial cells.

Unlike carcinomas in which epithelial cells have something known as a “basement membrane,” sarcomas do not have a “precancerous cell” stage and therefore screening tests for precancerous stages of the disease are not effective.

Rhabdomyosarcoma is a cancer of muscle cells, specifically skeletal muscles (striated muscles) which aid in the movement of our bodies. Historically, rhabdomyosarcoma is known as the “small round blue cell tumor of childhood” based on the color the cells turn with a specific dye used on tissues.

Altogether, this cancer is the third most common type of childhood solid cancer (not including blood-related cancers such as leukemia). It is slightly more common in boys than girls and is also slightly more common in Asian and African American children than in white children.

Types

Rhabdomyosarcoma is broken down into three subtypes:

• Embryonal rhabdomyosarcoma accounts for 60 to 70% of these cancers and occurs most often in children between the ages of birth and 4 years of age. This type is again broken down into subtypes. Embryonal tumors may occur in the head and neck area, the genitourinary tissues, or other regions of the body.
• Alveolar rhabdomyosarcoma is the second most common type and is found in children between the ages of birth and 19. It is the most common type of rhabdomyosarcoma seen in teens and young adults. These cancers are often found in the extremities (arms and legs), genitourinary area, as well as the chest, abdomen, and pelvis.
• Anaplastic (pleomorphic) rhabdomyosarcoma is less common and is seen more often in adults than in children.

Sites

Rhabdomyosarcomas may occur anywhere in the body where skeletal muscle is present. The most common areas include the head and neck region, such as orbital tumors (around the eye), and other regions, the pelvis (genitourinary tumors), near the nerves exciting the brain (parameningeal), and in the extremities (arms and legs).

Signs and Symptoms

The symptoms of rhabdomyosarcoma vary widely depending on the site of the tumor. Symptoms by region of the body may include:

• Genitourinary tumors: Tumors in the pelvis may cause blood in the urine or vagina, a scrotal or vaginal mass, obstruction, and bowel or bladder difficulties.
• Orbital tumors: Tumors near the eye can cause swelling around the eye and bulging of the eye (proptosis).
• Parameningeal tumors: Tumors near the spinal cord may present with problems related to the cranial nerve they are near such as facial pain, sinus symptoms, bloody nose, and headaches.
• Extremities: When rhabdomyosarcomas occur in the arms or legs, the most common symptom is a lump or swelling that doesn’t go away but increases in size.

Incidence

Rhabdomyosarcoma is uncommon and accounts for roughly 3.5% of cancers in children. Around 250 children are diagnosed with this cancer in the United States each year.

Causes and Risk Factors

We don’t know exactly what causes rhabdomyosarcoma, but a few risk factors have been identified. These include:

• Children with hereditary syndromes such as neurofibromatosis type 1 (NF1), Li- Fraumeni syndrome, Costello syndrome, pleuropulmonary blastoma, cardio-facial cutaneous syndrome, Noonan syndrome, and Beckwith-Wiedermann syndrome
• Parental use of marijuana or cocaine
• High birth weight

Diagnosis

The diagnosis of rhabdomyosarcoma usually begins with a careful history and physical exam. Depending on the location of the tumor, imaging studies such as an X-ray, CT scan, MRI, bone scan, or PET scan may be done.

In order to confirm a suspected diagnosis, a biopsy usually needs to be done. Options may include a fine needle biopsy (using a small needle to aspirate a sample of the tissue), a core needle biopsy, or an open biopsy may be done. Once the pathologist has a sample of the tissue, the tumor is looked at under the microscope and other studies are often done to determine the molecular profile of the tumor (looking for gene mutations responsible for the growth of the tumor).

To check for metastatic disease, a sentinel node biopsy may be done. This test involves injecting a blue dye and radioactive tracer into the tumor and then taking a sample of the lymph nodes closest to the tumor which light up or are stained blue. A full lymph node dissection may also be needed if the sentinel nodes test positive for cancer. Further studies to look for metastases may include a bone scan, bone marrow biopsy, and/or a CT of the chest.

Staging and Grouping

The “severity” of a rhabdomyosarcoma is further defined by figuring out the stage or group of the cancer.

There are 4 stages of rhabdomyosarcoma:

• Stage I: Stage I tumors are found in “favorable sites” such as orbital (around the eye), head and neck, in the reproductive organs (such as the testes or ovaries), the tubes connecting the kidneys to the bladder (the ureters), the tube connecting the bladder to the outside (urethra) or around the gallbladder. These tumors may or may not have spread to lymph nodes.
• Stage II: Stage II tumors have not spread to lymph nodes, are no larger than 5 cm (2 1/2 inches), but are found in “unfavorable sites” such as any of the sites not mentioned under stage I.
• Stage III: The tumor was present in an unfavorable site and may or may not have spread to lymph nodes or be greater than 5 cm.
• Stage IV: A cancer of any stage or lymph node involvement that has spread to distant sites.

There are also 4 groups of rhabdomyosarcomas:

• Group I: Group 1 includes tumors that can be completely removed with surgery and have not spread to lymph nodes.
• Group 2: Group 2 tumors can be removed with surgery but there are still cancer cells present at the margins (on the edge of the removed tumor), or the cancer has spread to lymph nodes.
• Group 3: Group 3 tumors are those that have not spread, but are unable to be removed with surgery for some reason (often due to the location of the tumor).
• Group 4: Group 4 tumors include those that have spread to distant regions of the body.

Based on the above stages and groups, rhabdomyosarcomas are then classified by risk into:

• Low-risk childhood rhabdomyosarcoma
• Intermediate-risk childhood rhabdomyosarcoma
• High-risk childhood rhabdomyosarcoma

Metastases

When these cancers spread, the most common sites of metastases are the lungs, bone marrow, and bones.

Treatments

The best treatment options for rhabdomyosarcoma depend on the stage of the disease, the site of the disease, and many other factors. Options include:

• Surgery: Surgery is the mainstay of treatment and offers the best chance of long-term control of the tumor. The type of surgery will depend on the location of the tumor.
• Radiation therapy: Radiation therapy may be used to either shrink a tumor that is not operable or to treat the edges of the tumor after surgery to remove any remaining cancer cells.
• Chemotherapy: Rhabdomyosarcomas tend to respond well to chemotherapy, with 80% of these tumors decreasing in size with treatment.
• Clinical trials: Other methods of treatment such as immunotherapy drugs are currently being studied in clinical trials.

Coping

Since many of these cancers occur in childhood, both parents and the child must cope with this unexpected and frightening diagnosis.

For older children and teens living with cancer, there is much more support than in the past. From online support communities to cancer retreats designed specifically for children and teens, to camps for either the child or family, there are many options available. Unlike the school setting where a child may feel unique, and not in a good way, these groups include other children and teens or young adults who are similarly coping with something that no child should ever have to face.

For parents, there are few things as challenging as facing cancer in your child. Many parents would love nothing less than to change places with their child. Yet caring for yourself is never more important.

There are a number of in-person as well as online communities (online forums as well as Facebook groups) specifically designed for parents of children facing childhood cancer and even rhabdomyosarcoma in particular. These support groups can be a lifeline when you realize that family friends have no way of understanding what you are going through. Meeting other parents in this way can lend support while giving you a place in which parents can share the latest research developments. It's sometimes surprising how parents are often aware of the latest treatment methods even before many community oncologists.

Don't minimize your role as an advocate. The field of oncology is vast and growing every day. And nobody is as motivated as the parent of a child living with cancer. Learn some of the ways to research cancer online and take a moment to learn about being your own (or your child's) advocate for your cancer care.

Prognosis

The prognosis of a rhabdomyosarcoma varies greatly depending on factors such as the type of tumor, the age of the person diagnosed, the location of the tumor, and treatments received. The overall 5-year survival rate is 70%, with low-risk tumors having a survival rate of 90%. Overall, the survival rate has improved greatly over the last several decades.

A Word From Verywell

Rhabdomyosarcoma is a childhood cancer that occurs in skeletal muscles anywhere these muscles are located in the body. Symptoms vary depending on the particular site of the tumor as well as the best methods for diagnosing the tumor. Surgery is the mainstay of treatment, and if the tumor can be removed with surgery there is a good outlook for long-term control of the disease. Other treatment options include radiation therapy, chemotherapy, and immunotherapy.

While survival from childhood cancer is improving, we know that many children suffer from the late effects of treatment. Long-term follow-up with a physician familiar with the long-term side effects of treatment is essential to minimize the impact of these conditions.

For parents and children who are diagnosed, becoming involved in a support community of other children and parents coping with rhabdomyosarcoma is priceless, and in the age of the internet, there are now many options available.