Small swollen bump under the skin on my palm?

My wife has had this bump 'in' her hand for the past 2 months almost. We have tried popping it, and nothing comes out but clear liquid sometimes. It is located in the general area between her index finger and thumb on her palm. It started out small and progressively got worse, it was very tender and painful for her to touch it or to use anything with that hand. Just from observation it looked as if it was swelling like there was a splinter in her hand and it was just getting infected, BUT it had since disappeared (swelling and redness gone away), and returned 2 other times. Each time it turns the area red-ish and bruised looking very bad. If anyone knows another suggestion of what this could possibly be please help, and if you can email me I may be able to provide a picture of what it looks like exactly. Thanks for the help.