Immunohistochemistry on a mediastinal mass in a 25-year-old shows positivity for OCT3/4, SALL4, and CD30, but negativity for AFP and hCG. The most likely diagnosis is:

• A Yolk sac tumor
• B Choriocarcinoma
• C Mature teratoma
• D Embryonal carcinoma ✓

Explanation

Embryonal carcinoma characteristically expresses the pluripotency transcription factors OCT3/4 and SALL4, along with CD30 (a TNF receptor family member). AFP is a marker of yolk sac tumor, and hCG marks syncytiotrophoblasts of choriocarcinoma. Mature teratoma contains differentiated elements and is negative for all these markers.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.