Giant ganglion cyst of the quadriceps femoris tendon.

We present the case of a ganglion cyst with 11 x 3 x 2 cm dimensions originating from the quadriceps femoris tendon. The patient presented with palpable mass and chronic pain in the anterolateral thigh region. The pain increased with walking. Ultrasonography and computed tomography revealed a cystic, well defined lesion in the vastus lateralis muscle. The patient was operated on and the cyst excised; it was seen to be a ganglion cyst. The patient is asymptomatic 6 months after surgery. This is a very rare localization for a giant synovial cyst, and preoperative diagnosis is a challenge for the surgeon.