Cystic hygroma in the quadriceps muscle: a sanguine diagnosis for knee pain.

Reported here is a 28-year-old female who presented with severe right knee pain and swelling nearby the joint. Ultrasonography, magnetic resonance imaging and eventually surgery were performed. She was diagnosed to have a cystic hygroma in the vastus lateralis muscle. This is the first patient of a cystic hygroma in the quadriceps muscle.