A ganglion cyst is a fluid or jelly filled sac of tissue underneath your skin. These typically arise at joints or on tendons in the foot and ankle. Although non-cancerous, they can produce a significant amount of pain or discomfort. Patients may notice they continue to increase in size and may continue to fluctuate. Depending on the location, a cyst may press upon a nerve or reduce motion at a joint, causing further discomfort and disability. You may experience sharp, burning, tingling, dull or aching pain. https://www.myfootspecialist.com/foot-surgery/ganglion-cysts/