This article reviews common pediatric urologic cancers involving the genitourinary system. Rhabdomyosarcoma may occur in the bladder, prostate, paratesticular regions, vagina, or uterus. Some of these locations, such as the paratesticular region, have a more favorable outcome. Benign neoplasms account for the majority of pediatric testicular tumors and most are managed with testis-sparing surgery. Most genitourinary malignancies are expected to have a good outcome. One focus of treatment is organ preservation but not at the expense of a good oncologic outcome. Late sequelae of anticancer therapy are a concern and every attempt is made to decrease the intensity of tumor treatment.
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Patients with disorders of sexual development are at increased risk for gonadal tumors. Children with a history of undescended testis have a slight increased risk of testis cancer after puberty.
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Benign lesions, such as mature teratomas and epidermoid cysts, should be managed with testis-sparing surgery.
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Yolk sac tumor should be managed with radical inguinal orchiectomy. Greater than 90% are stage I at diagnosis; thus, chemotherapy and retroperitoneal lymph node dissection are rarely indicated.
Genitourinary rhabdomyosarcoma
Epidemiology, Pathology, and Staging
Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in infants and children, with 15% to 20% arising from genitourinary sites, including prostate, bladder, paratesticular, vagina, and uterus. There is a bimodal age distribution with a peak incidence in the first 2 years of life and again at adolescence. A genetic predisposition is found in the Li-Fraumeni syndrome and neurofibromatosis. Embryonal RMS is the most common subtype that includes sarcoma botryoides, a polypoid variety that occurs in the bladder or vagina. Alveolar RMS, the second most common form, has a worse prognosis with a higher rate of local recurrence. As with most solid tumors, tumor stage is most predictive of clinical outcome. Preoperative studies to determine the extent of disease include chest CT, CT or MRI of the primary site, bone scan, and bone marrow biopsy. The most common site of metastatic spread of RMS is the lung. Unfavorable prognostic factors include unfavorable sites (eg, bladder or prostate, presence of distant metastases at diagnosis, involved regional lymph nodes, primary tumors greater than 5 cm, and age less than 1 or greater than 10 years old).
Treatment
The treatment of RMS has evolved from radical surgical excision. Several advances have been made by cooperative group studies, including identification of prognostic factors (histology, site, biology, and extent of disease) ; reduction or elimination of radiation therapy for special groups or sites ; reduced need for radical surgery leading to increased bladder salvage ; and elimination of routine lymphadenectomy for some patients with localized paratesticular RMS.
Bladder and prostate rhabdomyosarcoma
RMS of the bladder or prostate often presents with symptoms of urinary obstruction, including urinary frequency, stranguria, acute urinary retention, and hematuria. Tumors of the bladder usually occur as a botryoid form and grow intraluminally ( Fig. 1 ), whereas prostatic RMS tends to present as a solid mass and often has a poorer prognosis. On physical examination, an abdominal mass may be present. CT/MRI can delineate the extent of tumor and evaluate pelvic and retroperitoneal nodes. Cystoscopy can confirm the diagnosis and facilitates transurethral biopsy.
The treatment of bladder/prostate RMS is focused on preserving an intact bladder. Unfortunately, many of these tumors are not amenable to partial resection. Most centers recommend chemotherapy and radiation before surgery, with the exception of those children amenable to partial cystectomy at diagnosis, to allow for bladder sparing after multimodal treatment. Pooled data from multiple cooperative groups have demonstrated 5-year overall survival rate of 84% for patients with nonmetastatic embryonal bladder/prostate RMS. In the International Rhabdomyosarcoma Study (IRS)-IV, the bladder was able to be retained in 55 patients. At last follow-up of the IRS-IV patients, however, only 36 patients (40%) had no relapse and a normally functioning intact bladder. Thus, although radiation is important to prevent local treatment failure, radiation may affect bladder function in children. Urodynamic evaluation of bladder function after radiation has shown a reduced bladder capacity and abnormal voiding patterns.
The concern regarding bladder function has led some groups to explore treatment of bladder/prostate RMS without routine radiation therapy. These include risk-based approaches that use response to chemotherapy to stratify patients and determine the need for radiation therapy. There are reports of high relapse rates after complete remission by imaging and biopsy, however. Thus, close follow-up of patients with apparent complete remission is indicated.
Paratesticular rhabdomyosarcoma
Paratesticular RMS accounts for 7% to 10% of genitourinary RMS tumors with the peak age of presentation between 1 and 5 years old. Presentation is often a unilateral painless mass or scrotal swelling that is distinct from the testis. At diagnosis, 60% to 80% of paratesticular tumors are stage I compared with 13% of RMS overall. More than 90% of paratesticular RMS are embryonal in histology and have a good prognosis. Abdominal CT is needed to rule out extension to retroperitoneal lymph nodes that occurs in up to 20% of patients.
Initial treatment is radical inguinal orchiectomy. The current Children’s Oncology Group (COG) protocols recommend that children 10 years and older have an ipsilateral retroperitoneal lymph node dissection as part of routine staging before chemotherapy. Patients with positive lymph nodes require intensified chemotherapy and nodal irradiation. With current multimodal treatment, survival rates of 90% are expected.
Vaginal and uterine rhabdomyosarcoma
Vaginal RMS generally presents in the first few years of life with vaginal bleeding, discharge, or a vaginal mass. Uterine RMS may present as a tumor originating from the cervix with vaginal bleeding or mass or as a tumor originating in the uterine body presenting as an abdominal mass. Vaginal and uterine lesions generally have embryonal or botryoid histology and have an excellent prognosis.
In the past, patients were frequently treated with anterior pelvic exenteration. With the development of effective chemotherapy, attempts to preserve the vagina and uterus have become a priority and definitive surgery is delayed until after an initial course of chemotherapy. Once an adequate response is demonstrated, repeat biopsies are performed. If there is persistence of disease, delayed tumor resection is performed with partial vaginectomy or vaginectomy with hysterectomy. Unfortunately, treatment of pelvic RMS in female patients may result in significant late complications secondary to multimodal therapy, including vaginal stenosis, ureteral obstruction, intestinal stricture or fistula, and ovarian failure.
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Embryonal rhabdomyosacroma is the most common subtype and may exist as the sarcoma botryoides forms, which grows in hollow organs, such as the bladder or vagina.
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Sixty percent to 80% of paratesticular RMSs are stage I at presentation. Patients older than 10 years, however, are at higher risk for retroperitoneal relapse and thus should undergo staging with ipsilateral retroperitoneal lymph node dissection before chemotherapy.
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Goals of treatment include organ preservation; thus, initial neoadjuvant chemotherapy and/or radiation are performed to improve rates of organ sparing after urgical resection.
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