Q: I have a small lump under my skin on the inside of my left thumb. It’s not movable and is my normal skin color. It’s located on the inside, where the knuckle is. What is it?
A: It doesn’t sound very serious. If it’s near a joint, it is probably a ganglion cyst — a benign fluid collection that is connected to the synovial sac of the joint. These can resolve on their own or, if they get bothersome, they can be aspirated with a needle and syringe.
A less likely possibility would be a rheumatoid arthritis nodule, but only if you’ve had joint pain or stiffness. You should have a doctor look at it, just to make sure about this. But I think ganglion cyst is the most likely diagnosis.
— Answer from Dr. Chip, a physician on JustAnswer.
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