Giant Cell Tumour of Tendon Sheath Info
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Giant cell tumour of tendon sheath — a benign, slow-growing lump on fingers/thumb, often treated with excision.
What you're feeling
You might notice a small, firm lump on the side of your finger or thumb that grows slowly over weeks or months. Often, this mass is painless at first, but as it gets larger, it can become tender or make your finger feel stiff. You may find it difficult to bend or straighten your finger fully, or the lump might get in the way when you try to make a fist. Sometimes, the mass feels like a hard pea under the skin, and you might notice it more when you are gripping objects or typing.
What's actually happening
This condition is called a Giant Cell Tumor of the Tendon Sheath. It is a benign growth that starts in the lining of the tendon sheath—the soft tissue tube that protects and guides your finger tendons as they move. Think of your tendons like ropes that pull your fingers, and the sheath as the smooth sleeve that keeps them gliding easily. In this condition, cells in that lining start to grow too much, forming a small, round mass.
These tumors are not cancer. They do not spread to other parts of your body. However, they can be locally aggressive, meaning they can push against nearby structures like your bone or nerves. The growth is driven by a specific protein called colony-stimulating factor 1, which signals the body to create more of these cells. While the exact trigger is unknown, these tumors are most common in adults between the ages of 30 and 50. They are slightly more common in women than men. You might notice the lump on the palm side of your finger, near the joint, where the tendon sheath is tightest.
What we can do about it
Your surgeon will discuss the best path forward based on the size of the lump, how much it bothers you, and whether it is affecting your finger's movement.
Watchful Waiting If the lump is small, painless, and not stopping you from using your hand, your doctor might suggest simply watching it. Many of these tumors grow very slowly, and some may not cause any problems for years. You would return for check-ups to ensure the mass isn't growing rapidly or damaging the joint.
Surgery If the lump is painful, growing, or making it hard to move your finger, surgery is usually the recommended treatment. The goal is to remove the entire tumor and the affected lining of the tendon sheath. This is typically done as an outpatient procedure, meaning you go home the same day.
The surgeon will make a small incision on the side of your finger to access the lump. Because the tumor is often attached to the tendon sheath, the surgeon must be careful to remove all the abnormal tissue while protecting the tendon itself. In some cases, a small microscope or magnifying glasses are used to see the tiny details and ensure nothing is left behind.
After surgery, you will likely wear a small splint for a few days to keep the finger comfortable. Most people can start gentle movement of the finger within a week or two to prevent stiffness. Full recovery usually takes a few weeks, and you can return to normal activities as the swelling goes down.
Recurrence Even with careful surgery, there is a chance the tumor could come back. This happens in about 10 to 20 percent of cases, particularly if the tumor was large or located near the joint. If it returns, a second surgery is often successful. In rare cases where the tumor is very difficult to remove without causing damage, your surgeon might discuss other options, though these are uncommon for tumors in the hand.
When to see someone
You should make an appointment with a hand specialist if you notice a new lump on your finger that does not go away after a few weeks. Seek care sooner if the lump grows quickly, becomes painful, or if you notice your finger is getting stiff or difficult to bend. If the lump changes color, becomes red and warm, or if you develop a fever, contact your doctor immediately, as these could be signs of infection rather than a tumor.
