Anterior knee schwannoma

Peripheral nerve tumors are relatively uncommon with schwannomas being the most common type. Schwannomas are usually benign encapsulated tumors composed of neoplastic Schwann cells that generally do not transform to malignancy. Many are discovered incidentally as solitary tumors. The cause is unknown. Most occur spontaneously, while some develop in association with genetic disorders such as neurofibromatosis type 2 or schwannomatosis. Schwannomas can occur anywhere in the body. They affect all ages, with peaking incidence between ages 20 and 50 years, without predilection to sex or race. Many are asymptomatic; however, presenting signs and symptoms, such as paresthesia and pain, are due to mass effect and direct nerve invasion. Diagnosing includes combinations of thorough physical examination, imaging modalities such as magnetic resonance imaging and surgical biopsy. Treatment depends on factors such as location of the tumor and severity of symptoms. Asymptomatic patients are treated conservatively while symptomatic patients undergo surgical resection with favorable prognosis.