Alveolar Rhabdomyosarcoma


Alveolar rhabdomyosarcoma is a malignancy that mainly affects children. Around 3% of all the cases of malignancies in children are due to ARMS [1, 2].

What is Alveolar Rhabdomyosarcoma?

Rhabdomyosarcoma is considered to be the most usual type of sarcoma in children. Sarcomas are malignancies of soft tissues in the body and it usually affects areas such as muscles, tendons and cartilages. Although it may begin in any part of the body, it commonly begins in the muscles that are attached to bones and involves in body movement [1, 2, 3].

There are 2 main types of rhabdomyosarcoma that is found in children: embryonal, alveolar and anaplastic rhabdomyosarcoma. The embryonal type is the most common among the 3 types and the malignancy occurs in the head, neck or genitals of the child. Alveolar rhabdomyosarcoma most occurs in the arms, legs, chest and abdominal area [1, 2, 3].

Alveolar rhabdomyosarcoma (ARMS) may affect all age groups but it is mostly found in older children and teenagers. The cells of the muscles that is affected by this condition is similar to the normal muscle cells of a 10-week-old fetus. ARMS is more aggressive than the embryonic type and requires a more intensive treatment regimen. The prognosis is dependent on several factors and the 4-year survival rate for localized and metastatic ARMS are 65% and 15% [1, 2, 3]. Figure 1 shows the thigh of a child with ARMS.

Alveolar Rhabdomyosarcoma



Figure 1- Alveolar rhabdomyosarcoma of the thighs

Staging

The extent of ARMS is described in terms of stages [4].


Stage I

The malignancy is still confined to its original location and has not yet spread to other body parts [4].

Stage II

A few tumors that are less than 5cm in diameter are present but there are no tumor cells found in the lymph nodes [4].

Stage III

It is either a tumor that is smaller than 5cm but has already spread to its surrounding lymph node or a localized mass which diameter is greater than 5cm but it has not spread to other body parts [4].

Stage IV

The tumor has already metastasized to other organs of the body such as the lungs, liver and bones when the condition has been diagnosed [4].

Risk Factors

As with other malignancies, the etiology of ARMS is still unknown but based on several studies, there are risk factors which may increase the likelihood of developing ARMS. Most of these factors are inherited diseases such as: Costello syndrome, Noonan syndrome, pleuropulmonary blastoma and Li-Fraumeni syndrome. The exposure from radiotherapy due to previous cancer treatments may lead to the development of sarcoma but it won’t develop until after 10 years after the treatment. Chemicals such as vinyl chloride, herbicides and dioxins are also linked to ARMS [1, 3, 5].

Signs and symptoms

ARMS may develop in any part of the body and the signs and symptoms that may be experienced will depend on the part that is affected. Usually, the individual will notice a swelling or lump that is developing in the arm, leg or torso. This lump will continuously grow and will not go away. It may be painless but there are instances where it will become painful [3].

Other signs and symptoms which may be experienced include the presence of blood in the urine, changes in urinary and bowel pattern and bleeding from the throat, nose and vagina [1].

Alveolar Rhabdomyosarcoma Images

Diagnosis

Health history and physical examination

The focus of the health history is the symptoms that are felt by the patients. Any pain that is felt must be characterized to identify the source and frequency. The physical examination will assess the lump or swelling that have developed along with other possible symptoms that are related to the location of the tumor [1, 6].

Blood tests

A blood test may be requested by the physician to assess the involvement of other organs. Abnormalities in the CBC and liver function test will indicate metastasis into the bone marrow and liver. Renal and liver function tests must also be assessed before considering the possibility of chemotherapy [1, 6].


Imaging tests

If ARMS is diagnosed in its later stage, it may have metastasized to other organs. CT (Computed Tomography) scans and MRI (Magnetic Resonance Imaging) scans will be able to provide a visualization of any organ involvement in the body [1, 6].

Biopsy

A tissue sample may be obtained by the physician for analysis. It will be examined under the microscope to identify the cellular changes that have occurred. The result of the biopsy will confirm the diagnosis of ARMS [1, 6].

Alveolar Rhabdomyosarcoma Histology

Treatment

Surgery

Before a surgery is considered, its effect to the body function must be considered. If the surgery will not have a major effect on the patient, the tumor will be removed by performing a wide local excision. In this method, the tumor along with a margin of healthy cells are removed. A margin of normal cells is included to ensure that no cancer cells will be left behind. In some instances, it is impossible to surgically remove all the cancer cells. In this case, the patient will need to undergo another treatment regimen to ensure that no cancer cells are left[1, 2, 6].

Radiation therapy

In this method, a machine produces high energy beams to kill the cancer cells. There are machines who will be able to produce the radiation based on the shape of the tumor. The radiation is also delivered in a way that damage to healthy tissues will be avoided [1, 2, 6].

Chemotherapy

Chemotherapy uses drugs that are either given orally or intravenously to eliminate the cancer cells. This therapy is recommended on its own or in combination with other methods to decrease the possibility of ARMS from recurring [1, 2, 6].

Survival Rate and Prognosis

The 5-year survival rate for children who are diagnosed with alveolar rhabdomyosarcoma is about 80% for those who have developed no metastases and have underwent both surgery and chemotherapy. Patients who have already developed metastases have a 30% 5-year survival rate. Relapses are less common after 5 years but around 9% may relapse after 10 years. The relapse occurs in patients who have residual tumor cells in unfavorable sites after they underwent a surgery.

There are several factors that may affect the prognosis of a patient with alveolar rhabdomyosarcoma. These factors include the original site of tumor, age of the patient at the time of diagnosis, the size of the tumor, involvement of regional lymph nodes and the presence of metastases.

References

  1. National Cancer Institute. (2015, December 18). Childhood Rhabdomyosarcoma Treatment (PDQ®)–Patient Version. Retrieved from National Cancer Institute: http://www.cancer.gov/types/soft-tissue-sarcoma/patient/rhabdomyosarcoma-treatment-pdq
  2. American Cancer Society. (2014, November 21). Rhabdomyosarcoma. Retrieved from American Cancer Society: http://www.cancer.org/cancer/rhabdomyosarcoma/detailedguide/rhabdomyosarcoma-key-statistics
  3. Diede, S. (2013, May 13). Types of Childhood Cancer: Alveolar Rhabdomyosarcoma. Retrieved from St. Baldrick’s Foundation: http://www.stbaldricks.org/blog/post/types-of-childhood-cancer-alveolar-rhabdomyosarcoma/
  4. Stanford’s Children’s Health. (2015). Rhabdomyosarcoma. Retrieved from Stanford’s Children’s Health: http://www.stanfordchildrens.org/en/topic/default?id=rhabdomyosarcoma-90-P02743
  5. Macmillan Cancer Support. (2014, April 1). Rhabdomyosarcoma. Retrieved from Macmillan Cancer Support: http://www.macmillan.org.uk/cancerinformation/cancertypes/softtissuesarcomas/typesofsofttissuesarcomas/rhabdomyosarcoma.aspx#DynamicJumpMenuManager_6_Anchor_3
  6. Cripe, T. P. (2016, May 1). Pediatric Rhabdomyosarcoma. Retrieved from Medscape: http://emedicine.medscape.com/article/988803-overview

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