Intramuscular Ganglion of the Quadriceps Femoris
A 17-year-old male patient visited our institution with a complaint of a painful movable mass on the lateral distal aspect of the right femur that was not caused by trauma. The mass had been slowly growing for 6 months and started to cause increasing pain from one month ago. The patient had no history of other systemic disease. In the physical examination, a firm and movable mass with a size of a quail egg was palpated in the lateral distal aspect of the right femur. The size of the mass did not change during joint motion. Neither muscle weakness and numbness nor abnormal sensation was observed in the lower leg. In the absence of abnormal findings on radiography, ultrasound was performed, in which a cystic tumor approximately 4.1×2.5 cm in size was identified in the quadriceps femoris (). A magnetic resonance imaging (MRI) was considered unnecessary because it had a relatively distinct border and was well-encapsulated. Exploration and excision of the mass were performed under the assumption of a vascular lesion or a lipoma within the vastus lateralis of the quadriceps femoris. Noninvasive methods such as aspiration and steroid injection could be an option, but surgical excision was our treatment of choice in order to reduce the possibility of recurrence. Intraoperatively, spindle-shaped swelling was observed and a firm mass was palpated in the vastus lateralis of the quadriceps femoris. The mass could be dissected with ease from the surrounding tissue and had a stalk as other ganglion cysts. When the muscle sheath was removed, the mass was found to originate from the muscle, not from the muscle sheath. In the naked eye, the intramuscular cystic mass was 3.4×2.2×1.4 cm in size, weighed 4.7 g, and had some muscle tissue on its smooth surface (). When dissected upon excision, clear jelly-like fluid was noted in the sac. The biopsy results showed that the cystic wall was composed of fibrous tissue, lacked a synovial lining, and had muscular tissue on the surface, which led us to the diagnosis of an intramuscular ganglion cyst (). Rehabilitation was started after two weeks of splint immobilization. There has been neither recurrence nor complications for the 1 year and 6 months of follow-up period.