Pediatrics: Practice Question

A 7 year old male patient is found to have a retroperitoneal tumor. Biopsy shows small round blue cells. Which of the following profiles is most supportive of an Ewing sarcoma / primitive neuroectodermal tumor?
  1. NSE+, SYN+, CD99+, PAS+, TTF-1 -
  2. CD99+, CD45+, TdT+, CD-3+, WT-1 -
  3. WT-1 +, CK +, desmin +, EMA+, CD45 -
  4. Desmin+, myogenin+, actin+, CD99 -
  5. CD99+, CD45+, TdT+, CD-79a+, WT-1 -
Show Answer and Explanations

NSE+, SYN+, CD99+, PAS+, TTF-1 - — Correct answer

Correct. This staining profile supports a diagnosis of Ewing sarcoma / PNET.

CD99+, CD45+, TdT+, CD-3+, WT-1 -

Incorrect. This immunoprofile is most supportive of lymphoblastic lymphoma, T-cell, which is more common than B cell in children.

WT-1 +, CK +, desmin +, EMA+, CD45 -

Incorrect. This immunoprofile is most supportive of Wilms tumor. The blastema is positive for WT-1 and desmin, the epithelium is positive for WT-1, keratin and EMA, and the stroma is weakly WT-1 positive and can show staining by differentiation.

Desmin+, myogenin+, actin+, CD99 -

Incorrect. This profile is most supportive of rhabdomysarcoma, which can show CD99 positivity and cytoplasmic but not nuclear WT-1 positivity.

CD99+, CD45+, TdT+, CD-79a+, WT-1 -

Incorrect. This immunoprofile is most supportive of B-cell lymphoblastic lymphoma.

Summary

Summary: Ewing sarcoma: NSE+, SYN+, CD99+, PAS+, and translocation t(11;22) Fli-1 - EWS.
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