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Findings: 2.5 x 1.5 x 1.5 cm paratesticular mass with heterogeneous echo texture. Right testicle is normal in size and echo texture with normal blood flow through it.

Diagnosis: Paratesticular embryonal rhabdomyosarcoma

Differential Diagnosis:Neoplasm: Paratesticular cystic adenomatoid tumor (by far the most common), leiomyoma, fibroma, adrenal rest, cord lipoma, cholesteatoma, malignant tumor (rhabdomyosarcoma being the most common. Polyorchidism, sperm granuloma, epididymitis, scrotal calculi/long standing hydrocele/torsion.

Discussion: Rhabdomyosarcoma: This is the most common pediatric soft tissue sarcoma and the only common pediatric tumor that can occur in any non-CNS site. Its incidence is approximately 10% of all childhood soft tissue tumors. It shows both hematogeneous and lymphangitic spread. There is no significance gender or race predilection. Peak incidence occurs between 2 and 6 years with a second peak at 15-19 years. Occurrence during the neonatal period carries a poor prognosis.

The tumor is thought to arise from primitive rhabdomyoblasts or totipotential mesenchymal cells and therefore can occur anywhere in the body outside the CNS. Three major histologic types are recognized: 1) Embryonal (<50%, carries the best prognosis, a common subtype is sarcoma botryoides). 2) Alveolar (worst prognosis, usually involves the extremities in adolescents). 3) Pleomorphic (seen mostly in the adult population, involving the trunk and extremities, rarely seen in children).

Location is age dependent: Pelvis and GU tract (39%), head and neck (31%), perianal, bile duct lesions are more commonly seen in infancy and childhood. Trunk, extremity, and uterine lesions are more common in adolescents.

Staging: Preop radiologic assessment and histologic evaluation of the surgical margins and lymph nodes is required.

• GpI Localized disease, completely resected, no nodal involvement.
  • a. Tumor confined to the muscle or organ of origin
  • b. Tumor infiltration outside this structure
• GpII Localized or regional disease with total gross resection
  • a. Primary tumor grossly resected, with microscopic residual disease, regional nodes negative
  • b. Completely resected primary tumor
  • c. Resected primary tumor, with evidence of microscopic residual disease and positive nodes (all resected)

• GP III Incomplete resection or biopsy, with residual unresected disease
• GP IV Distant metastatic disease present at diagnosis (regional nodes excluded).

References:
1. Taveras JM, Ferrucci JT: Radiology. JB Lippincott Co., 1995, Vol. 4, Ch 134, P. 14.

2. Kirks DR: Practical Pediatric Imaging. Little Brown & Co., 1991, p. 1032.

3. Rosai J: Surgical Pathology. C.V. Mosby Co., 1989. Vol. 2, p. 977.

4. Sabiston DC: Textbook of Surgery. WB Saunders, Co., 1991, pp. 1181-1182.

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