Solitary Neurofibroma at the Popliteal Fossa in a Patient With Leg Numbness—A Case Report

Neurofibromas are common peripheral nerve sheath tumors. Symptoms vary according to the site, including skin discoloration, disfiguration or neurologic deterioration. Neurofibromas cannot be seen on plain X-ray film unless they involve the bone and cause intraosseous lytic lesions. Ultrasonography plays an important role in the examination of soft tissue mass because it is inexpensive and has the advantage of being real-time for initial screening. In this study, we present a patient with a palpable mass over her right popliteal fossa. The texture of the mass was solid, without pulsation or fluctuation during palpation examination. There was no bruit on auscultation. Ultrasonography showed a well-defined, oval, solid and hypoechoic mass containing anechoic areas. Magnetic resonance imaging revealed the location of the tumor enveloped by the tibial nerve. An electrodiagnostic study supported the impression of entrapped neuropathy at the right popliteal area. After surgical excision of the mass, pathological findings confirmed the diagnosis of neurofibroma. This case report is clinically significant due to the rare site of the neurofibroma.