Cellular smears show branching tissue fragments composed of parallel arays of spindle cells. The nuclei are thin and elongated, and cytoplasm is ill-defined. Scattered large, hyperchromatic atypial nuclei are seen within some of the tissue fragments. No necrosis is seen. Mitotic figures are not identified.

Note: An important clue to the daignosis is that the FNA is usually exquisitely painful, and the patient will make it known in no uncertain terms!  

If cell block were available, S100 (+), Desmin (-). 

Diagnosis: Schwannoma