Giant cell tumour of tendon sheath

What is a giant cell tumour of tendon sheath?

Giant cell tumour of tendon sheath is a non-cancerous tumour that commonly occurs in the fingers of the hand. It can also involve the large joints of the body such as the knee and elbow. Joints connect two bones together and are important for movement. Although a giant cell tumour of tendon sheath is non-cancerous, a small number of them can grow back at the same location over time. This tumour most commonly affects people in their 30s and 40s and occur more commonly in females.

What is a tendon?

Tendons are tough bands of tissue that connect a muscle to bone and are important for movement. Tendons are similar to ligaments that connect two bones together and are important for stability. Tendons are covered and protected by a thin layer of tissue called a tendon sheath. The tendon sheath is filled with lubricating fluid that allows tendons to move smoothly and freely.

How do pathologists make this diagnosis?

Giant cell tumour of tendon sheath is typically diagnosed after a small sample of tissue is removed in a procedure called a biopsy or they are completely removed in a procedure called an excision or resection. They are then examined by a pathologist under the microscope.

The tumour is made up of two kinds of cells:

1. Mononuclear cells – These are small round cells with a single nucleus. The nucleus is the part of the cell that holds most of the cell’s genetic material (DNA).
2. Osteoclast-like giant cells – These are very large cells that have more than one nucleus.

Your pathologist will look for both of these types of cells when examining your tissue sample under the microscope.

If the diagnosis was made after a biopsy, you may undergo another surgery to remove the tumour completely. After the tumour is removed completely it will be sent to pathology where a pathologist will examine the tissue to confirm the original diagnosis.

by Osama Khan MD and Bibianna Purgina MD FRCPC, updated December 24, 2020