Diagnosis: Mediastinal Tumors
• The photomicrograph shows a lesion with the characteristic appearance of a neurilemmoma (benign schwannoma).
• Neurilemmomas are diffusely and strongly positive for S100 protein.
• Although not specific for schwannoma, given this location and this histologic appearance, an S100 immunostain should suffice.
• This illustrates the importance of context in evaluating immunostaining results.
