Fine-needle aspiration of epithelioid malignant peripheral nerve sheath tumor (epithelioid malignant schwannoma).

The epithelioid variant of malignant peripheral nerve sheath tumor (MPNST), also known as malignant epithelioid schwannoma, is a relatively rare and recently characterized clinicopathologic entity. The epithelioid variant of MPNST shares many clinical features with conventional MPNST but is characterized by different histologic and cytologic features. These include a distinctive nesting pattern and an abundance of cytoplasm not seen in histology of conventional nerve sheath tumors. Cytologically, the epitheliod variant shows a propensity to cellular discohesiveness and a plasmacytoid or epitheliod appearance that is in contradistinction to the spindled appearance of the usual MPNST. Herein, we report our experience with fine-needle aspiration (FNA) of two epithelioid malignant schwannomas and discuss the FNA cytologic differential diagnosis.