Rhabdomyosarcoma

Rhabdomyosarcoma is a rare type of cancer that develops in muscle tissue and primarily affects children and teenagers, though adults can also be diagnosed. This aggressive disease requires a combination of treatments and can occur anywhere in the body, making early recognition of symptoms crucial for better outcomes.

Table of contents

• What is rhabdomyosarcoma?
• Types of rhabdomyosarcoma
• Who is affected?
• Signs and symptoms
• Causes and risk factors
• How is it diagnosed?
• Treatment approaches
• Outlook and survival

What is rhabdomyosarcoma?

Rhabdomyosarcoma is a rare type of cancer that starts as a growth of cells in soft tissue, which includes muscles and other tissues that support and connect organs throughout the body^[1]. It is believed to originate from primitive cells called mesenchymal cells that typically develop into skeletal muscle tissue^[4].

Although rhabdomyosarcoma most often starts in muscle tissue, it can begin in many places throughout the body^[1]. Common locations include the head and neck area, the urinary system such as the bladder, reproductive organs including the vagina, uterus and testes, and the arms and legs^[1].

Rhabdomyosarcoma is the most common type of soft tissue sarcoma in children^[3]. Between 400 and 500 people in the United States receive this diagnosis each year^[2]. While it predominantly affects young people, only 1% to 2% of these cancers are found in adults^[4].

• Skeletal muscles
• Head and neck
• Urinary system (bladder)
• Reproductive organs (vagina, uterus, testes)
• Arms and legs
• Abdomen (belly)

Types of rhabdomyosarcoma

There are several distinct types of rhabdomyosarcoma, each with different characteristics and patterns of occurrence^[3].

Embryonal rhabdomyosarcoma is the most common type, occurring most often in the head and neck area or in the genital or urinary organs, though it can develop anywhere in the body^[3]. This type primarily affects children under age 10 and has the best prognosis^[4]. The cells in this type are similar to developing muscle cells of a 6- to 8-week-old embryo^[5].

Alveolar rhabdomyosarcoma occurs most often in the arms or legs, chest, abdomen, genital organs, or anal area^[3]. This type typically affects older children, teenagers, and young adults between the ages of 20 and 35^[2]. Alveolar rhabdomyosarcoma is aggressive, meaning it spreads quickly soon after it develops^[2].

Spindle cell/sclerosing rhabdomyosarcoma has several subtypes. The spindle cell type occurs most often in the area around the testicles. One subtype is more common in infants and is found in the trunk area. Another can affect children, adolescents, and adults, is often found in the head and neck area, and tends to be more aggressive^[3].

Pleomorphic rhabdomyosarcoma is the least common type in children but typically affects adults ages 50 and older^[2]. It can develop anywhere in the body but mostly affects the legs, and also appears in the arms, chest, belly, and parts of the head and neck^[2].

Who is affected?

Rhabdomyosarcoma accounts for about 3% of all childhood cancers^[1]. The disease shows distinct age patterns, with more than half of cases occurring in children younger than 10 years old^[1]. There is a peak in incidence during early childhood, specifically in children under 4 years old^[5].

Rhabdomyosarcoma is slightly more common in males than females^[5]. Children between the ages of 1 and 9 years tend to have a better outlook than children 10 years of age and older or younger than 1 year^[23].

Most cases of rhabdomyosarcoma are sporadic, meaning they occur without a clear inherited cause. However, the disease can be associated with certain rare inherited conditions^[4]. No particular race or ethnic group appears to have an unusually high rate of this cancer^[5].

Signs and symptoms

Signs and symptoms of rhabdomyosarcoma depend on where the cancer starts in the body^[1]. Sometimes symptoms may not appear until the tumor is very large, and the first sign might be a lump or swelling that keeps getting bigger or does not go away, which may be painful^[3].

When the cancer is in the head or neck area, symptoms may include headache, bleeding in the nose, throat or ears, tearing, bulging or swelling of the eyes, or crossed-eyes^[1]. A tumor in the ear may cause earache or discharge^[2].

If the cancer is in the urinary or reproductive system, symptoms may include a mass or bleeding in the vagina or rectum, trouble urinating and blood in the urine, or trouble with bowel movements^[1]. In boys, there may be a fast-growing mass or lump around the testicles^[2].

When the cancer is in the arms or legs, symptoms may include swelling or a lump in the arm or leg, and possibly pain in the affected area if the cancer pushes on nerves or other areas of the body^[1]. A tumor in the belly can cause belly pain, constipation, or vomiting^[2].

Rhabdomyosarcoma symptoms may resemble less serious conditions. Many health issues can cause symptoms like nosebleeds, vomiting or lumps and bumps and may not be symptoms of rhabdomyosarcoma^[2]. However, you should contact a healthcare provider if you or your child have symptoms or changes that don’t go away or seem to be getting worse^[2].

Causes and risk factors

Rhabdomyosarcoma happens when immature muscle cells change, becoming cancerous cells that multiply and create tumors^[2]. In most cases, the cause of rhabdomyosarcoma is not known^[3].

Certain genetic mutations, including a change that creates the fusion gene PAX/FOX01, may cause a type of rhabdomyosarcoma^[2]. People with certain inherited disorders have an increased risk of developing the condition^[2].

Risk factors for rhabdomyosarcoma include having the following inherited diseases: Li-Fraumeni syndrome, Dicer1 syndrome, Neurofibromatosis type 1 (NF1), Costello syndrome, Beckwith-Wiedemann syndrome, and Noonan syndrome^[3]. Additional conditions that may increase risk include cardiofasciocutaneous syndrome^[2].

Children who had a high birth weight or were larger than expected at birth may have an increased risk of embryonal rhabdomyosarcoma^[3]. Having a risk factor does not mean that you will get cancer, and not having risk factors doesn’t mean that you will not get cancer^[3].

How is it diagnosed?

Rhabdomyosarcoma diagnosis usually begins with a physical exam^[14]. A healthcare provider will ask about your or your child’s symptoms and family medical history to learn if anyone has an inherited disorder that increases the risk of rhabdomyosarcoma^[2].

Diagnostic tests that are done depend in part on where the cancer forms^[3]. Tests may include imaging tests such as X-rays, CT scans (computed tomography scans), MRI scans (magnetic resonance imaging), PET scans (positron emission tomography scans), and bone scans^[14]. These imaging tests make pictures of the inside of the body and help show the location and size of the tumor^[14].

A biopsy is a procedure to remove a sample of tissue for testing in a lab^[14]. A biopsy for rhabdomyosarcoma needs to be done in a way that won’t cause problems with future surgery. For this reason, it’s a good idea to seek care at a medical center that sees many people with this type of cancer^[14].

Types of biopsy procedures used to diagnose rhabdomyosarcoma include needle biopsy, which uses a needle to remove tissue samples from the cancer, or surgical biopsy, where surgery is needed to remove a larger sample of tissue^[14]. The biopsy sample goes to a lab for testing, where doctors called pathologists will test the cells for cancer^[14]. Other special tests give more details about the cancer cells, and your healthcare team uses this information to make a treatment plan^[14].

Treatment approaches

Rhabdomyosarcoma treatment most often combines chemotherapy, surgery, and radiation therapy^[14]. Which treatments your healthcare team suggests depends on where the cancer is and the size of the cancer^[14]. Because the treatment plan is complicated and prolonged, all patients should be referred to a center with personnel who are skilled in caring for children with cancer^[16].

Treatment is tailored to a patient’s risk group. Patients are categorized according to their risk, which takes into account the location of the tumor and the results of testing and surgery^[16]. The standard chemotherapy regimen for patients with rhabdomyosarcoma is the combination of vincristine, actinomycin, and cyclophosphamide or ifosfamide^[12].

Surgery is performed when feasible to completely remove the primary tumor^[4]. Children with tumors that can be completely removed usually have a better outlook^[23]. Chemotherapy is used to control disease spread, even if no evidence of spreading is present on imaging, because most patients have been found to have very small amounts of cancer spread in studies^[4].

Radiotherapy is used to treat most high and intermediate-risk patients^[4]. With early detection and timely treatment, most children make a full recovery^[7]. Currently, treatment is multimodal, combining surgery, when feasible, chemotherapy, and in many cases radiation^[4].

The majority of patients with localized rhabdomyosarcoma can be cured. However, the long-term outcomes in patients with metastatic rhabdomyosarcoma (cancer that has spread to distant parts of the body) remain poor^[12]. Despite aggressive multimodality treatment, less than 20% of patients with metastatic disease are able to be cured^[4].

Outlook and survival

The outlook for rhabdomyosarcoma depends on many factors. Only a doctor familiar with a child’s medical history, the type, stage and characteristics of the cancer, the treatments chosen and the response to treatment can put all of this information together with survival statistics to arrive at a prognosis^[23].

Important factors that affect prognosis include the age at diagnosis, where the tumor started, tumor size, whether the cancer has spread, if the tumor can be completely removed, and the type of rhabdomyosarcoma^[23].

Children with cancer that has already spread to distant parts of the body when it is diagnosed have a poorer prognosis^[23]. The five-year survival rate for low-risk rhabdomyosarcoma is approximately 80-95%^[21]. The majority of rhabdomyosarcoma cases are intermediate risk with a 50-70% survival rate^[21]. However, once the cancer has spread to distant sites, the survival rate drops to 20-30%^[21].

Alveolar tumors tend to be more aggressive and have a poorer prognosis than embryonal tumors^[23]. Research into diagnosis and treatment have greatly improved the outlook for people diagnosed with rhabdomyosarcoma, and more and more people are living for years after a rhabdomyosarcoma diagnosis^[1].

Rhabdomyosarcoma can come back after treatment^[2]. Nearly all recurrences of rhabdomyosarcoma occur within three years of diagnosis^[21]. The survival of rhabdomyosarcoma patients has improved due to collaboration among healthcare professionals, leading to advancements in diagnosis and management approaches^[4].