Rhabdomyosarcoma (RMS) of the genitourinary tract is a rare form of cancer most frequently affecting pediatric populations. This soft tissue sarcoma is most likely to be diagnosed in children under the age of six, although it's possible for older individuals to be affected as well. RMS accounts for around 3 percent of all childhood cancers, according to the American Cancer Society.
Ultrasound is the most common first-line diagnostic test performed when RMS is suspected. In some cases, aggressive management of RMS is indicated based on the organs affected and the patient's presenting symptoms. Doctors should discuss fertility preservation strategies depending on the patient's diagnosis, prognosis and whether or not they may wish to have children in the future.
Rhabdomyosarcoma Types
Researchers have identified three major histologic subtypes of RMS:
- Alveolar rhabdomyosarcoma (ARMS) typically arises from precursor cells within skeletal muscle tissue. While most cases occur in the extremities, it is possible for ARMS to develop within the genitourinary tract. ARMS is more likely to affect older children, teens and adults than younger patients. This fast-growing cancer usually requires intensive treatment.
- Embryonal RMS is the most common type of RMS, and usually affects children within the first five years of life. In general, this form of cancer has a favorable prognosis, especially with early diagnosis and treatment. One subtype of embryonal RMS, known as botryoid RMS, occurs most frequently in the bladder or vagina. Typically, botryoid RMS manifests as a grape-like cluster of tissue, which may be visible upon examination of the patient. In many cases, botryoid RMS has a more favorable prognosis compared to the more common form of embryonal RMS.
- Pleomorphic RMS, also known as anaplastic or undifferentiated rhabdomyosarcoma, is extremely rare in children. Pathological examination reveals that these cancers are sarcomas, but other distinguishing cellular features are missing. In most cases, pleomorphic RMS grows quickly and requires prompt treatment with intensive methods.
In children, the genitourinary tract is the second most common site of RMS development. Doctors are most likely to encounter symptoms such as vaginal bleeding, hematuria, dysuria or palpable pelvic masses. In pediatric gynecological patients, RMS most frequently occurs in the cervix, vagina and corpus uterus. However, this form of cancer may also affect the vulva, ovaries and uterus NOS (not otherwise specified).
Ultrasound's Role in Diagnosing Rhabdomyosarcoma
Ultrasound is usually the first imaging test of choice for evaluating suspected RMS, although other imaging tests, such as CT, MRI and positron emission tomography (PET) scans may be of more value diagnostically. Ultrasound has several advantages over other imaging tests, such as its typically wider availability, lower cost, high resolution and ease of assessing the extent and vascularity of any genitourinary masses.
Depending on their age and healthcare literacy, pediatric patients may be hesitant to undergo an ultrasound procedure. Talking with patients and their caregivers using age-appropriate language can encourage cooperation and assuage any fears associated with the procedure. In some cases, it may be appropriate to allow young patients to touch the probes before you use them. Gynecologists should answer any patient or caregiver questions using easily understood terms.
2D Versus 3D Ultrasound
Both 2D or 3D ultrasound may help in the initial evaluation of RMS. In most cases, tumors appear as heterogeneous masses with both variable solid and cystic elements.
Imaging protocols should be tailored to the needs of each patient. Initially, it may be most beneficial to perform a 2D transabdominal ultrasound examination of the pelvis, which is useful for identifying tumors while helping to ensure as little discomfort to young patients as possible. But while 2D imaging easily shows tumors, it may not be as useful for evaluating suspected tissue invasion related to the primary tumor.
3D ultrasound offers views of the sagittal, axial and coronal planes, providing clinicians with a more comprehensive picture of the uterus, bladder, vagina and other genitourinary areas. This type of scan is more useful for evaluating a tumor's relationship to other structures, such as the vaginal fornices or the cervical lip. Color Doppler can be a useful addition for visualizing tumor vasculature and blood flow. Ultrasound findings can be confirmed with other imaging tests such as MRI if necessary.
Ultrasound-Guided Biopsy
In some cases, it may be necessary to perform a biopsy to further evaluate tissue samples for evidence of cancer. In pediatric patients especially, ultrasound-guided biopsy is the preferred method of obtaining samples compared to primary resections. In most cases, fine needle aspiration or core needle biopsies are sufficient for obtaining a sample.
Considering Fertility Preservation
For some young patients with cancer, fertility preservation is a key component of the treatment plan. Treatment for genitourinary cancers generally consists of chemotherapy, radiation therapy, surgery or a combination of all three. These treatments may greatly affect a young patient's future chances of achieving pregnancy.
In recent years, gynecologists have become increasingly interested in fertility-sparing interventions for gynecologic rhabdomyosarcoma. Some forms of RMS, especially those affecting the cervix, may be treated with a combination of:
- Cervical conization.
- Robotic-assisted radical trachelectomy.
- Multi-agent chemotherapy.
A study published in Gynecological Oncology Reports showed that these three interventions, used in combination, successfully preserved fertility in three young women with embryonic RMS of the cervix. Doctors may select patients for these types of procedures depending on the location of the cancer and the patient's desire to avoid hysterectomy.
Early diagnosis using ultrasound and other imaging methods is essential for better prognostic outcomes among patients with rhabdomyosarcoma. For younger patients, ultrasound offers greater comfort while still allowing clinicians to accurately identify tumors or other suspected changes to the gynecological tract. This technology is also helpful for obtaining tissue samples or studying the vasculature of any detected tumors.
Fertility sparing treatments may be considered for some young patients based on their diagnosis, prognosis or wishes for starting a family later in life. Clinicians should use their best judgment and experience to help determine which patients may benefit from fertility-sparing treatments, and discuss these options in an approachable and age-appropriate way.
