Genitourinary: Practice Question

A 69-year-old male presents with an expansile bladder mass. If the mass is found to be a sarcoma, which of the following diagnoses is most likely?
  1. Angiosarcoma
  2. Dedifferentiated liposarcoma
  3. Rhabdomyosarcoma
  4. Well-differentiated liposarcoma
  5. Leiomyosarcoma
Show Answer and Explanations

Angiosarcoma

Incorrect. Though possible, primary angiosarcomas of the urinary bladder are exceptionally rare. When present, they typically stain for vascular markers by immunohistochemistry, including ERG, CD31, and CD34.

Dedifferentiated liposarcoma

Incorrect. Liposarcomas are the most common primary sarcomas of the paratestis. Whether well-differentiated or dedifferentiated, they typically express CDK4 and MDM2 by immunohistochemistry, and show MDM2 amplification by FISH.

Rhabdomyosarcoma

Incorrect. The most common primary sarcoma of the urinary bladder in pediatric patients is rhabdomyosarcoma. The most common primary sarcoma of the urinary bladder in adults is leiomyosarcoma.

Well-differentiated liposarcoma

Incorrect. Liposarcomas are the most common primary sarcomas of the paratestis. Whether well-differentiated or dedifferentiated, they typically express CDK4 and MDM2 by immunohistochemistry, and show MDM2 amplification by FISH.

Leiomyosarcoma — Correct answer

Correct. The most common primary sarcoma of the urinary bladder in adults is leiomyosarcoma. It has a high rate of metastasis, and the prognosis is poor. The tumors are typically strongly and diffusely positive for muscle markers desmin and SMA/SMSA by immunohistochemistry. The most common primary sarcoma of the urinary bladder in pediatric patients is rhabdomyosarcoma.

Summary

Summary: The most common primary sarcoma of the urinary bladder in adults is leiomyosarcoma. It has a high rate of metastasis, and the prognosis is poor. The tumors are typically strongly and diffusely positive for muscle markers desmin and SMA/SMSA by immunohistochemistry. The most common primary sarcoma of the urinary bladder in pediatric patients is rhabdomyosarcoma. Liposarcomas are the most common primary sarcomas of the paratestis.
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