Also known as: neurilemmoma
- Benign subcutaneous tumor, most often seen in adults
- Most common on the limbs and head and neck
- Usually cured by simple excision, with rare recurrences
- May be multiple in neurofibromatosis type II
- Round, encapsulated mass in the subcutaneous fat (rarely intradermal)
- Classically biphasic, with Antoni A and Antoni B areas:
- Antoni A:
- More cellular
- Tightly packed spindle cells with tapered, wavy nuclei
- Verocay bodies: hypocellular area flanked on two sides by palisading cells
- Occasional nuclear pleomorphism (a degenerative change) and mitoses can be seen.
- Hyalinization or dystrophic calcification may be present.
- Antoni B:
- More hypocellular
- Scattered spindle or stellate cells in a myxoid background
- Focal chronic inflammation
- Small hyalinized blood vessels
- Degenerative changes may include microcystic change and hemosiderin deposition.
- S-100 is positive, in keeping with the Schwann cell origin.
- Rare tumors with hybrid features of schwannoma and neurofibroma exist.
- Several subtypes exist, which will be discussed under their respective headings.