Nerve Sheath Tumors

摘要

Schwannoma: Schwannoma is a benign nerve sheath tumor composed of Schwann cells. They are typically encapsulated and arise sporadically in the superficial or, less often, the deep soft tissues of the head and neck and the limbs. Schwannomas arise occasionally in the retroperitoneum, posterior mediastinum, or as a pelvic mass (usually larger tumors). A small subset of these tumors occurs in the gastrointestinal tract and parenchymal organs or involving cranial nerves. Schwannomas occur commonly in adults up to 50 years of age, but may be seen in all age groups. Approximately 10% are associated with syndromes such as neurofibromatosis type 2, schwannomatosis, or multiple meningiomas. Schwannomas are common targets for fine-needle aspiration (FNA) examination. Many patients experience sharp pain when their tumors are punctured, a pain which occasionally radiates along a nerve. This sign can provide a valuable clue to the diagnosis but is not entirely specific, and maybe encountered in the aspiration of other soft tissue lesions situated close to a peripheral nerve. Smears from schwannomas vary with respect to cellularity but are often hypercellular, containing irregular tissue fragments of spindle cells embedded in a fibrillary stroma.