Popliteal schwannoma mimicking baker cyst: an unusual case.

Schwannoma, also known as neurilemoma, is the most common tumour of peripheral nerves. Although it is the most common tumour of peripheral nerves, it is seldom seen in adult population. We present a very rare case of schwannoma in an unusual localization. The presented case concerns a 58-year-old patient with a slowly growing popliteal mass and neuralgia for 6 months. A mass originating from a nerve or compressing a nerve was thought in the differential diagnosis. Ultrasonographic and magnetic resonance imaging revealed a heterogenous, well-defined solid mass that seems to originate from tibial nerve. Surgical excision and histopathological examination confirmed the diagnosis of schwannoma. Diagnosis of the neurilemmoma originating from lower extremity peripheral nerves may be delayed because the mass can be misdiagnosed as baker cyst or the symptoms of the patient can be thought as a result of lumber disc herniation.