Which marker is NOT part of the IHC panel for primary spindle sarcoma (second question)?

• A. MPNSY
• B. MFH
• C. Desmin
• D. Glial Fibrillary Acidic Protein

Answer: (D)

The main idea here is how immunohistochemistry is used to identify the lineage of a spindle cell tumor. When evaluating primary spindle sarcomas, pathologists use markers that reveal mesenchymal origin and possible differentiation, such as desmin to look for muscle lineage. Glial fibrillary acidic protein, on the other hand, marks glial cells in the nervous system and is used to diagnose neural or glial tumors like gliomas. Because primary spindle sarcomas arise from soft tissue mesenchyme, GFAP positivity would not fit the typical panel and would suggest a different kind of tumor. That’s why GFAP is not included in the IHC panel for primary spindle sarcoma.