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Diagnosis and Treatment of Paratesticular Rhabdomyosarcoma

Rhabdomyosarcoma of the paratesticular region is a rare malignant tumor derived from mesenchymal cells.

Epidemiology

1–3% of all pediatric cancers are rhabdomyosarcomas, with an incidence of 3–7 cases per 1 million children, depending on age. 20% of rhabdomyosarcomas originate in the genitourinary tract, with the most common localization in the prostate, urinary bladder, and paratesticular, less common uterus and vagina.

Pathology of Paratesticular Rhabdomyosarcoma

Paratesticular rhabdomyosarcoma arises from the distal spermatic cord and invades the testicle and surrounding tissues.

• Embryonal rhabdomyosarcoma: the most common type of urogenital rhabdomyosarcoma in children, sometimes with grapevine-like growth (Sarcoma botryoides) and a relatively good prognosis.
• Alveolar rhabdomyosarcoma: more common in extremities than urogenital rhabdomyosarcoma in children, has a poor prognosis, especially with PAX3-FOXO1 gene fusion.
• Rare rhabdomyosarcomas: spindle cell/sclerosing rhabdomyosarcoma and pleomorphic rhabdomyosarcoma.

Signs and Symptoms

Unilateral painless scrotal mass. Palpation: paratesticular mass, which is often distinct from the testis.

Diagnostic Workup of Paratesticular Rhabdomyosarcoma

• Scrotal ultrasound
• MRI of the abdomen
• Chest CT

Treatment of Paratesticular Rhabdomyosarcoma

Treatment should be carried out within clinical trials to improve the treatment of this rare disease. After diagnosis, the patients are stratified to an appropriate study protocol in relation to the tumor stage and risk group. The following factors are considered: tumor location, tumor size, histology, grading, lymph node involvement, metastases, and results of surgical treatment. Study protocols are, e.g., Children's Oncology Group (COG), which is the successor of the Intergroup Rhabdomyosarcoma Study Group (IRSG) or European Cooperative Groups (SIOP).

IRS Grouping

IRS grouping is used by both COG and European study groups.

• Group I: localized tumor, completely resected.
• Group IIA: grossly resected tumor with microscopic residual disease.
• Group IIB: regional disease with lymph node metastases, completely resected with no evidence of microscopic residual disease, most distant lymph nodes without metastasis.
• Group IIC: regional disease with lymph node metastases, grossly resected but with evidence of microscopic residual disease or metastases in most distant lymph nodes.
• Group III: incomplete resection or biopsy with macroscopic residual disease.
• Group IV: distant metastases.

Inguinal Radical Orchiectomy

Inguinal radical orchiectomy is the initial treatment step since most present with a resectable tumor stage. Depending on the tumor stage or previous scrotal surgery, hemiscrotectomy may be appropriate.

Adjuvant therapy with COG protocol:

Children without visible metastases in staging and younger than ten years receive adjuvant chemotherapy without prior retroperitoneal lymphadenectomy. In children older than ten years, retroperitoneal lymphadenectomy is recommended before adjuvant chemotherapy. For visible metastases (IRS groups III–IV), multimodality therapy with higher toxicity is necessary.

Prognosis:

50% relapse within two years after orchiectomy without adjuvant therapy. With adjuvant treatment, survival rates of 90% are possible if a complete tumor resection is possible (IRS groups I–II). The 5-year survival rate for patients in IRS group IV is below 50%.

Related diseases

• Sarcoma of the bladder
• Sarcoma of the prostate

References

Ahmed, H. U.; Arya, M.; Muneer, A.; Mushtaq, I. & Sebire, N. J. Testicular and paratesticular tumors in the prepubertal population.
Lancet Oncol, 2010, 11, 476-483.

National Cancer Institute: Childhood Rhabdomyosarcoma Treatment (PDQ)–Health Professional Version https://www.cancer.gov/types/soft-tissue-sarcoma/hp/rhabdomyosarcoma-treatment-pdq

  Deutsche Version: Paratestikuläres Rhabdomyosarkom