[Neurilemmoma (schwannoma) of the oral cavity. A report of 2 clinical cases].

Neurilemmoma (schwannoma) is a benign, encapsulated perineural tumor of neuroectodermal derivation that originates from the Schwann cells of the neural sheath of motor and sensitive peripheral nerves; the etiology is still unknown. The tumor is normally solitary, smooth-surfaced, slow growing and generally asymptomatic. It may develop at any age and there is no gender predilection. Head and neck are one of the most frequent localizations, but intraoral development is quite uncommon. In this area the mobile portion of the tongue, and in a decreasing order, the palate, the cheek mucosa, the lip and gingiva are the most frequent locations. Although it origins from the nervous tissue, only in 50% of the cases a direct relation with a nerve is demonstrated. The term schwannoma has been attributed in the past either for neurofibroma and neurilemmoma. Their histogenesis remain anyway a controversial argument. Some authors think that both tumors originate from Schwann cells and perineural connective cells. Others think that the first one originate from perineural cells, while the latter from Schwann cells. Diagnosis is confirmed by microscopic examination. Neurilemmoma shows two different components: Antoni type A and Antoni type B tissue. The first one consists of Schwann cells arranged in compact, twisted bundles, associated with delicate reticulin fibres and spindle-shaped nuclei aligned in parallel rows forming a typical palisading pattern. Between the rows there are fine cytoplasmatic fibrils with acellular, eosinophilic masses called Verocay bodies. The second one is formed by irregularly arranged masses of elongated cells and fibers similar in appearance to neurofibroma, with areas of cystic degeneration and edema.(ABSTRACT TRUNCATED AT 250 WORDS)