Causes of hard bumps under the skin of your arm include ganglion cysts and giant cell tumors. Both are noncancerous, but these can be alarming without appropriate diagnosis. Problems caught early can be treated more sufficiently, so always seek medical attention if you notice changes or bumps on your skin.
Identification
Both ganglion cysts and giant cell tumors are identified as a mass within the skin. Approximately 80 to 90 percent of ganglion cysts form around the wrists, according to Sports MD. The size depends on the activity level of the affected joint, according to MayoClinic.com. Ganglion cysts and giant cell tumors are both firm and immobile. Giant cell tumors are normally painful, but ganglion cysts are usually not painful unless the cyst is placing pressure on nerves of the joint, according to MayoClinic.com.
Cause
The cause of both ganglion cysts and giant cell tumors is unknown. For ganglion cysts, osteoarthritis, which is arthritis caused by wear-and-tear is a common risk factor, according to MayoClinic.com. The more you use the joint associated with a ganglion cyst, the larger the cyst will grow. A giant cell tumor forms when a generation of mononucleara cells fuses together, according to Children's Hospital Boston.
Diagnosis
Both are diagnosed by first receiving a physical examination by a physician. If the bump is not painful, the physician may feel around the bump to determine if the bump moves under the skin. X-rays, ultrasounds or MRIs are all tools used to diagnose bumps under the skin.
Treatment
Treatment may not be needed for a ganglion cyst if immobilization can reduce their size. Ganglion cysts can also be numbed by a local anesthetic and then a needle and syringe used to aspirate fluid from the cyst. The fluid removed is a gelatinous material that resembles the fluid that lubricates the joints, according to SportsMD. Aspiration has a success rate of 30 to 50 percent, according to Sports MD. Surgery can also be used for ganglion cysts and is the only way to remove a giant cell tumor, according to BoneTumor.org.
Considerations
Although giant cell tumors are benign, they do pose the danger of spreading to the lungs, according to Children's Hospital Boston. Left untreated, a giant cell tumor can also cause a fracture since it can break through the bones external layers. If the tumor or cyst is surgically removed, there is always the risk of nerve or tendon damage that can lead to weakness, less range of movement and numbness, according to MayoClinic.com.
