Popliteal schwannoma mimicking baker cyst: an unusual case
Fifty-eight-year-old man presented to the outpatient clinic of orthopaedics department with the complaints of slowly growing mass on his right popliteal region and mild pain and intermittent paresthesia of right leg and right foot. The patient emphasized that the mass existed for 2 years but has grown in the last 6 months. On physical examination, 4 × 2 cm mobile, solid mass was palpable at the posterior of the knee. There was no erythema, warmth or ulceration and Tinel's sign was positive. Sensory and motor examinations of lower extremity were normal. Ultrasound imaging showed that the mass was solid and separate from the adjacent muscles and tendons. MRI showed well-defined solid, heterogenous, dense mass originating from the tibial nerve (Fig. ). Surgical exploration and excisional biopsy was performed. At prone position with longitudinal incision, popliteal region was explorated and tumoural mass originating from tibial nerve was dissected. Sheath of the nerve was incised longitudinally to minimize damage to the nerve fascicles and the mass was resected in en-bloc form by sharp dissection using the microscope with no complication. The patient was discharged at the post-op third day. At the third week of the operation, the patient was free of all complaints. Histopathological examination of the mass revealed hypocellular Antoni B and spindle-shaped Schwann cells containing Antoni A areas with nuclear palisading. Also immunohistochemical staining (S100+) confirmed the diagnosis of schwannoma.