Schwannoma/ Neurilemmomas:Its a benign neoplasm derived from Schwann cells.

Clinical feature: Age: any age from infancy to middle age. No sex predilection Location: 50% of these tumors arise in head neck region. In oral cavity dorsum of the tongue is the most common site. Others include palate, floor of the mouth, buccal mucosa and gingiva. Sometimes occurs in inferior alveolar nerve in mandible. Its a slowly enlarging mass of long standing associated with a nerve trunk. Any pain is due to pressure on the tumor on the adjacent nerve. The lesion is smooth, firm, exophytic and appears as a movable mass beneath the mucosa and sometimes tender of palpation. Occasionally the tumor arises centrally within the tumor arises centrally within the bone and produces bone expansion of cortical plate and considerable destruction. Bilateral neurilemmomas of auditory vestibular nerve is a characteristic feature of hereditary condition, neurofibromatosis type 2.

Histopathology: Uninodular masses are surrounded by fibrous capsule, consisting od epineurium and residual nerve fibers. Hallmark of schwannoma is pattern of alternating Antoni A and Antoni B areas , the amount Of these 2 areas may vary and they may blend imperceptibly or change abruptly. Antoni A area composed of compact spindle cell that usually have twisted nuclei, indistinct cytoplasmic border and occasionally clear intranuclear vacuoles. Usually arranged in short bundle. In highly differentiated Antomi A area there may be nuclear palisading (Adescriptivetermforalightmicroscopicappearanceofelongatedandcompressed,usuallyepithelialcells,perpendiculartoasurfacee.g.,abasementmembrane;palisadingisclassicfindinginbasalcellcarcinoma) whirling of cells and verocay bodies, formed by 2 compact rows of well aligned nuclei separated by fibrilar cell processes. Antoni B areas are far less orderly and less cellular. The spindle or oval cells arranged haphazardly in the loosely textured matrix, infiltrated by inflammatory cells and delicate collagen fibers. The large irregular spaced vessels become most conspicuous in the hypocelluar Antoni B area. The lumens are filled with thrombous material of various stages of organization and their walls are thickened by dense fibrosis. Occasionally schwannomas develop cystic space lined Schwann cells that assume round or epitheloid appearance, known pseudoglandular schwannomas.

Figure : Nuclear palisading and verocay body

Radiology: Central neurilemmomas present well defined unilocular or multilocular radiolucent area in the jawbone with expansion and distortion of the cortical plate. Large lesion may cause extensive bone destruction may even perforation of the cortical plate.

Neurofibroma:Its a benign neural tissue neoplasm arising from the perineural fibroblast

Subtypes: 1. Plexiform neurofibroma:irregularly expanded nerve bundles with nodular appearance, prominent myxoid matrix; associated with NF1.2. Diffuse cutaneous:traps adnexa, infiltrates into fat.3. Focal cutaneous.4. Intraneural.Clinical feature: Benign, common, spindle cell tumor; multiple tumors associated with neurofibromatosis type 1 Solitary tumor suggests patient does NOT have neurofibromatosis type 1 Malignant transformation rare in sporadic neurofibromas Age: can occur at any age No sex predilection Location: usually painless soft tissue swelling of the tongue and gingiva. Skin lesions may causes itching When associated with inferior dental and other nerves in the head neck region facial pain, deafness and paraesthesia may occur. Tumors are mobile laterally but not mobile in the line of the nerve. Not encapsulated, softer (more gelatinous) than schwannoma Superficial tumors are small, pedunculated nodules protruding from skin (molluscum pendulum) Deeper tumors are larger, may cause tortuous enlargement of peripheral nerves (plexiform neurofibromas)

Histopathology: Non-encapsulated Proliferation of all elements of peripheral nerves

Schwann cells with wire like collagen fibrils (wavy serpentine nuclei, pointed ends), stromal mucosubstances, mast cells, Wagner-Meissner corpuscles, Pacinian corpuscles, axons (highlight with silver or acetylcholinesterase stain, NSE, neurofilament), fibroblasts and collagen Perineurial cells in plexiform types, mitotic figures are rare Less of a fascicular pattern than fibromatosis May be infiltrative, have myxoid areas, contain melanin pigment, have epitheloid morphology Rarely has skeletal differentiation (neuromuscular hamartoma) No Verocay bodies, no nuclear palisading, no hyalinized thickening of vessel wallsSome other images of Neurofibroma:

Radiology:Radiologically neurofibroma of the jaw bone produces a relatively well demarked unilocular or multilocular radiolucent area, with expansion of the cortical plate and divergence of the roots.

Neurofibromatosis/ Von Recklinghausen disease:Neurofibromatosis type 1: Peripheral form of neurofibromatosis.It is inherited as a autosomal dominant trait with high rate of penetrance. Defect in neurofibromin gene at 17q11.2; protein is widely expressed tumor suppressor gene that downregulates p21 ras oncoprotein. Clinical feature: Multiple neurofibromas (plexiform, solitary); plexiform are relatively specific 6 or more caf-au-lait spots over nerve trunks, 1.5 cm or larger (cafe au lait spot: increase in melanin in epidermal basal layer, may overlie a neurofibroma, smooth delicate margins; solitary caf au lait spots are normal) Lisch nodules (pigmented iris hamartomas, 94% by age 6) 2-4x increased risk of other tumors (childhood CML, ganglioneuroma, meningioma, pheochromocytoma, rhabdomyosarcoma);; also acoustic neuroma (schwannoma), astrocytoma, gastric carcinoid, GIST, glomus tumor, lipoma, optic nerve glioma, Wilm tumor Nontumors: congenital malformations, fibrosing alveolitis, megacolon. There may be skeletal abnormalities (kyphoscoliosis, bone hypertrophy, pseudoarthrosis) Enlargement of fungiform papillae. Unilateral enlargement of tongue.Neurofibromatosis type 2:

Also known as NF2, acoustic neurofibromatosis. Autosomal dominant. Mutation in merlin gene at 22q12. Bilateral acoustic neuromas or multiple meningiomas, spinal cord ependymomas; also schwannosis (ingrowth of Schwann cells into cord), meningioangiomatosis (meningeal cells and blood vessel proliferation into the brain), glial hamartia (microscopic nodular collections of glial cells in cerebral cortex); Cafe au lait spots are rare or absent, but no Lisch nodules.

Histology: Composed of proliferation of delicate spindle cells with thin, wavy nuclei intermingled with neuritis in an irregular pattern as well as delicate intertwining connective tissue fibers. Melanocytes may be found, mast cells are common. Lesion may be well circumscribed. The caf-au-lait pigmentation microscopically reveals basilar melanosis without proliferation of melanocytes.Radiology: Enlargement of mandibular foramen. Enlargement of branching of mandibular canal. Concavity of the medial surface of the ramus. Increase in dimension of coronoid notch.