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 . a firm and movable mass with a size of a quail egg was palpated in the lateral distal aspect of the right femur . 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 4.12.5 cm in size was identified in the quadriceps femoris ( fig . 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 3.42.21.4 cm in size , weighed 4.7 g , and had some muscle tissue on its smooth surface ( fig . 2 ) . 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 ( fig . there has been neither recurrence nor complications for the 1 year and 6 months of follow - up period . ganglion cysts are the most common soft tissue lesions of the hand that are composed of a fluid - filled sac connected to a synovial sheath , a tendon sheath , or a tendon . some studies associate them with mucoid degeneration of soft tissues , outpouchings of tissues through defects in the joint capsule or tendon sheath , or a trauma3 ) . the most common area of occurrence is the radial side of the extensor digiti communis tendon on the dorsum , followed by the area between the flexor carpi radialis and the abductor pollicis longus tendons on the volar side of the wrist4 ) . ganglions cysts arise from joints in most cases and rarely from the tendon sheath , cartilage , cruciate ligaments , nerves , and muscles5 - 7 ) . although most of the ganglia around the knee joint are located in the tendon sheath or joint capsule , they can form in the meniscus , anterior cruciate ligament , posterior cruciate ligament , and common peroneal nerve9 ) . intraosseous ganglion cysts that are characteristically located in the epiphysis of long bones are mostly solitary and involve the distal end of the tibia . currently , there are only 2 reported cases of ganglion cysts in the quadriceps femoris that were diagnosed using plain radiography , ultrasound , and computed tomography . in our patient , the majority of ganglion cysts are palpable tender lumps without any accompanying symptoms . however , when a ganglion cyst exerts pressure on the nerves or blood vessels , pain , numbness , and muscle weakness may occur or tenderness and discomfort during joint motion may present from the initial stage . although ultrasound is a valuable diagnostic tool , it is limited in its ability to evaluate the relationship between a cyst and adjacent soft tissues . mri is essential for the differential diagnosis from other masses such as vascular lesions and lipomas . in our patient , mri was considered unnecessary because the mass was seen well - encapsulated with a distinct border on ultrasound . it is important to identify during surgery whether a lesion is a mass , has a connection with a joint , or is associated with intraarticular disease and to perform thorough excision in order to reduce the likelihood of recurrence . ganglia rarely recur with proper curative measures , but inappropriate treatment methods can result in a recurrence rate of 50%3 ) . the available treatment options range from non - surgical methods such as rupture by direct pressure , aspiration with or without a steroid injection , and draining using threads to surgical excision with or without arthroscopy . the cure rate of ganglion cysts has no association with gender , age , and size and location . nelson et al.4 ) reported that the cure rate was 94% after excision under general anesthesia or axillary nerve anesthesia , 84% after excision under local anesthesia with a tourniquet in place , and 65% after rupture by direct pressure or aspiration with a steroid injection . in the study by aydin et al.10 ) on 40 cases of excision of ganglion cysts of the hand , the recurrence rate was 22% , damage to the median palmar cutaneous nerve was observed in 10% , radial nerve damage was present in 5% , and joint stiffness occurred in 5% . they cautioned that the possibility of recurrence and other complications should be taken into consideration in determining a surgical option for the treatment of a ganglion cyst . intramuscular ganglion cysts are rare with only a few cases involving the hand present in the literature . , we described a case of an intramuscular ganglion cyst in the vastus lateralis of the quadriceps femoris that was successfully treated with excision without complications .