A 45-year-old man presents with slowly progressive unilateral hearing loss, tinnitus, and imbalance. MRI reveals a well-circumscribed, enhancing mass at the cerebellopontine angle extending into the internal auditory canal (ice-cream cone appearance). Histology shows alternating Antoni A (cellular with Verocay bodies) and Antoni B (loose myxoid) areas. Which immunohistochemical marker is most consistently positive in this tumor?
- A S100 ✓
- B GFAP
- C EMA
- D Synaptophysin
Correct answer: A. S100
Explanation
This describes a schwannoma (vestibular schwannoma/acoustic neuroma), the most common cerebellopontine angle tumor. Schwannomas are strongly and diffusely positive for S100. GFAP is positive in astrocytomas and ependymomas. EMA is positive in meningiomas and perineuriomas. Synaptophysin is a neuronal marker positive in neuroblastomas and gangliogliomas. Verocay bodies (palisading nuclei with anuclear zones) are characteristic of Antoni B areas.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.