Schwannoma, or neurilemmoma, is a rare benign tumor of bone. It accounts for less than 0.1%1 of all bone neoplasms. It occurs most often in the head, neck, and flexor surfaces of upper and lower extremities. Schwannomas are found at all ages but most commonly between age 20 and 50. Most
lesions are asymptomatic.
     Radiologically, schwannomas present as well-circumscribed lytic, expansile lesions with sclerotic borders.
     On gross examination, a schwannoma as is a soft pink to yellow encapsulated mass less than five centimeters in size. The lesion may have cysts or calcification.
     histologically, schwannomas have two distinct components. The Antoni A regions are highly ordered and cellular with spindle shaped Schwann cells that have poorly defined eosinophilic cytoplasm and basophilic nuclei. Verocan,T bodies are configurations of palisading cells that alternate with acellular eosinophilic areas. The Antoni B regions are much less cellular and are characterized by large thin walled vessels surrounded edematous stroma. Schwannomas stain positive for S100 and vimentin.
     Most lesions may be observed without surgery. Curettage is effective for symptomatic or large lesions.

1 Huvos, Andrew, Bone Tumors:Diagnosis. Treatment and Prognosis, W.B. Saunders, Co., 1991.

Fletcher, Christopher, Diagnostic Histopathology of Tumors, Churchill Livingstone, 1995.





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