Rhabdomyosarcoma

Rhabdomyosarcoma is an abnormal and unregulated growth of muscles that are attached to the bones. Children are generally affected by this condition.

There are four main types of rhabdomyosarcoma, namely embryonal, alveolar, spindle cell, and pleomorphic. The embryonal type of rhabdomyosarcoma is the most common. It develops most commonly in the head, neck, arms, legs, trunk, chest, abdomen, urinary organs, and reproductive organs.

Associated Anatomy

 Head, neck, and genitourinary organs.

Alternate Name

RMS, Soft tissue sarcoma

Rhabdomyosarcoma Signs and Symptoms

The common signs and symptoms of rhabdomyosarcoma are:

• Swelling that increases in size
• Headache
• Proptosis: bulging of the eyeball
• Difficulty in urinating
• Hematuria: the presence of blood in the urine
• Bleeding from orifices such as mouth, nose, and vagina.

Rhabdomyosarcoma Causes

The exact cause of rhabdomyosarcoma is unknown because it is a rare tumor.

It is hypothesized to develop due to genetic mutations. However, the gene causing this sarcoma is yet to be found.

Additional Type

There are two types of rhabdomyosarcoma, namely embryonal and alveolar. Embryonal rhabdomyosarcoma affects children below the age of 5. Alveolar variants can affect anyone.

Rhabdomyosarcoma Stages

Staging of rhabdomyosarcoma is done based on the size of the tumor, its location in the body, and metastasis.

• Stage 1: The tumor of any size found in genitourinary organs, gallbladder, eyes, head, or neck.
• Stage 2: The tumor is less than 5 centimeters in size but involves sites other than those mentioned in stage 1.
• Stage 3: The tumor may be more than 5 centimeters in size, and the lymph nodes are involved.
• Stage 4: The tumor has spread to the lungs, bone marrow, or bone.

Rhabdomyosarcoma Tests

Some of the most important diagnostic methods include:

• Computed Tomography ( CT) Scan: CT scan can confirm the spread of the tumor and the involvement of lymph nodes.
• Biopsy: Biopsy of the suspected tumor site can help in confirming the diagnosis. Bone marrow biopsy is taken to detect the extent of the spread of the tumor cells to the bone. The various biopsy techniques used to obtain the sample are fine needle aspiration biopsy, core needle biopsy, and open biopsy.

Other investigations that can supplement our findings are:

• Magnetic Resonance Imaging ( MRI)
• X-rays
• Positron emission tomography scan

(PET scan)

• Bone scan
• Lumbar puncture
• Cytogenetic analysis

Rhabdomyosarcoma Treatment

The following three types of treatments are usually advised to patients: surgery, chemotherapy, and radiotherapy. A few upcoming treatment modalities include immunotherapy and targeted therapy.

Rhabdomyosarcoma can be removed surgically by wide local excision of the tumor and the surrounding tissues. The type of surgery is chosen based on the system involved and the tumor’s response to radiotherapy and chemotherapy.

Radiation therapy uses high-energy X-rays to kill cancerous cells. Radiation therapy is unsuitable for patients of all age groups and cannot be given in cases where the tumor is situated in sensitive areas. Not all types of sarcomas respond equally to radiation therapy.

Chemotherapy includes the use of medicines to decrease the growth of malignant cells. It reduces the size of the tumor when it is given before surgery for removal of the tumor. The medications used for chemotherapy depend on the patient’s age and ability to tolerate the medicine. The dose of the medicine depends on the stage of the tumor.

Newer techniques can be used to treat rhabdomyosarcoma. These include immunotherapy and targeted therapy. Immunotherapy is an upcoming modality that focuses on the patient’s immune system to fight against cancerous cells. Targeted therapy helps to limit the spread of cancerous cells by killing the cells while causing little or no harm to the normal cells. A few examples of targeted therapy include mTOR inhibitors such as Sirolimus and tyrosine inhibitors such as palbociclib.

Rhabdomyosarcoma Risk Factors

• Li-Fraumeni Syndrome: A condition in which there is a mutation of a gene (TP 53)
• Neurofibromatosis Type 1: A condition in which there are tumors involving nerves in the skin and brain.
• Gardner’s Syndrome: includes malignant growth in the stomach or bowel.
• Beckwith-Wiedemann Syndrome: It involves defects in the abdominal wall and an increase in the tongue and other organs.
• Costello Syndrome: occurs due to mutation of the HRAS gene. It affects multiple organs of the body.

Possible Complication

Treatment of rhabdomyosarcoma can have side effects in children. A few of the most important ones are changes in teeth, eyes, gastrointestinal system, mood and behaviour, and the emergence of secondary cancers in the long term. The most important complication is metastasis to other organs.

Rhabdomyosarcoma Prevention

Primary Prevention

Because the exact cause of the tumor is unknown, there aren't any measures to prevent rhabdomyosarcoma. Lifestyle changes or environmental modifications do not prevent rhabdomyosarcoma. 

Secondary Prevention

Even after successfully completing the treatment, follow-up should be regularly done to prevent the onset of secondary tumors. CT scans and MRI scans are usually advised to detect the recurrence of the tumor. Physiotherapy can help the patient to regain strength.

Differential Diagnosis

Rhabdomyosarcoma is diagnosed on the basis of the patient’s medical history, clinical assessment, and specific investigations such as imaging and biopsy. It can be differentiated from a few other types of cancers. All probable differential diagnoses are also cancers such as Wilms tumor, Ewing sarcoma, neuroblastoma, pheochromocytoma, liposarcoma, osteosarcoma, acute myelocytic leukaemia, acute lymphoblastic leukaemia, and non-Hodgkin lymphoma.

Most of these different cancers would also differ in their signs and symptoms from rhabdomyosarcoma. Yet, often they are found to be too similar in their presentation. Under such circumstances, further investigations would help with the correct diagnosis to differentiate rhabdomyosarcoma from these cancers.

Epidemiology

The epidemiology studies of rhabdomyosarcoma show that it is the most common type of soft tissue sarcoma in children and adolescent age groups. More than 50% of soft tissue cancers in children are rhabdomyosarcomas. Almost 1% of all tumors in adults are rhabdomyosarcomas. It is slightly more prevalent in males than females, with a 1.3:1 ratio.

Prognosis

Expected Prognosis

The outcome of rhabdomyosarcoma depends on the following factors: age of the patient, site of origin, size of the tumor, and the type of the tumor. Apart from these factors, it also depends on the type of treatment taken, abnormalities in genes, and metastasis to different parts of the body. Adults and adolescents have a poorer prognosis as compared to children. Embryonal rhabdomyosarcomas have a more favourable prognosis.

Natural Progression

If left unchecked, rhabdomyosarcoma will continue to grow and spread. The spread of cancer is known as metastasis. The most common metastasis sites for rhabdomyosarcoma are metastasis to the lung, bone marrow, and bone. If the tumor continues to grow, it may also lead to complications such as cardiomyopathy, pulmonary failure, and renal electrolyte wasting. Such complications will lead to multiple organ failures and can be fatal. There is also a possibility of recurrent rhabdomyosarcoma. The five-year survival rate of rhabdomyosarcoma is 72%.

Pathophysiology

The pathophysiology of rhabdomyosarcoma involves disruption of the mesenchymal cell growth. However, the exact mechanism and changes that cause this abnormal cell growth are not clearly known.