Mediastinum: Practice Question

A 45-year-old patient without a known cancer history presents with only a mediastinal mass and a biopsy demonstrates squamous cell carcinoma. Which immunoprofile is suggestive of thymic carcinoma?
  1. AE1/AE3+, synaptophysin-, chromogranin-, p40+
  2. AE1/AE3+, CD5-, CD117-, p40-, TTF1+
  3. AE1/AE3+, CD5+, CD117+, p40+, TTF1-
  4. AE1/AE3+, synaptophysin+, chromogranin+, p40-
  5. AE1/AE3+, CD5-, CD117-, p40+, TTF1-
Show Answer and Explanations

AE1/AE3+, synaptophysin-, chromogranin-, p40+

Incorrect. This immunoprofile is supportive of a diagnosis of squamous cell carcinoma from any organ and doe not help support a thymic origin for the squamous cell carcinoma diagnosis.

AE1/AE3+, CD5-, CD117-, p40-, TTF1+

Incorrect. This immunoprofile can be seen in lung adenocarcinoma.

AE1/AE3+, CD5+, CD117+, p40+, TTF1- — Correct answer

Correct. A large proportion of thymic carcinomas are positive for CD5 and CD117. They are also positive for keratin AE1/AE3 and can be p40 positive if they demonstrate squamous differentiation.

AE1/AE3+, synaptophysin+, chromogranin+, p40-

Incorrect. This immunoprofile is consistent with neuroendocrine not squamous cell carcinoma.

AE1/AE3+, CD5-, CD117-, p40+, TTF1-

Incorrect. A large proportion of thymic carcinomas are positive for CD5 and CD117.

Summary

Summary: In the right clinical context, CD5+, CD117+, and keratin+ is supportive of a diagnosis of thymic carcinoma.
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