You answered: Schwannoma

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Cytopathology:

• The smears reveal loose clusters of cells in a myxoid background
• The cells are oval and spindle-shaped; some have slightly bent nuclei
• There is moderate variation in nuclear size and shape. Some nuclear palisading is noted

Discussion:

• Schwannoma, also known as neurilemoma, is a benign, encapsulated tumour of Schwann cells found throughout the peripheral nervous system. They are commonly found in the head and neck region
• Aspiration biopsy is often unusually painful
• Treatment is simple surgical excision
• Tumour cells strongly express S100 protein and vimentin
• Histologically, schwannomas often have cellular and less cellular areas refered to as Antoni A and Antoni B areas respectively
• Antoni A areas may contain regions of bundles of spindle shaped Schwann cells with palisading nuclei surrounding a central fibrillar core known as Verocay bodies (not present in this case)
• Antoni B areas contain few randomly arranged Schwann cells within loose myxoid stroma
• Cytologic differential diagnosis:
• Pleomorphic adenoma may be suggested by the myxoid stroma and spindle cells. Confident diagnosis of PA requires identification of epithelial and/or myoepithelial cells in a metachromatic, usually fibrillar, stroma
• Nodular fasciitis may have spindle cells and myxoid stroma. A history of rapid growth is usually noted. Unlike Schwannoma the bland appearing spindle cells have wispy bipolar cytoplasmic processes and tend not to form Antoni A and B areas. Often a background of chronic inflammation is present
• The spindle cell variant of myoepithelioma may mimic Schwannoma but does not usually have a significant stromal component

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References:

Demay RM. The Art & Science of Cytopathology: Chicago: ASCP Press, 1996; 585-587, 669-673.

Faquin WC, Powers CN. Cytologic Evaluation of Salivary Gland Aspirates: A Case-Based Approach with Histologic Correlation. American Society of Cytopathology 53rd Annual Scientific Meeting. San Diego, CA, November 4-9, 2005.

Gray W, McKee GT. Diagnostic Cytopathology. 2nd Edition. Elsevier Science Limited 2003; 311, 884-896.