Bilateral Mirror-Symmetrical Giant Cell Tumor of the Tendon Sheath in the Foot and Ankle: A Case Report.

Giant cell tumor of the tendon sheath is a slowly growing benign tumor. It usually arises from the tendon sheath and periarticular soft tissue of small joints. However, it may infrequently involve the large joints emerging around the knee, elbow, and hip joints. Giant cell tumor of the tibialis tendon sheath is rarely reported in the foot and ankle joint. Here, we report the first case in the medical literature of bilateral mirror-symmetrical giant cell tumor of the tendon sheath in the foot and ankle. A 12-year-old male presented with a bilateral and mirror-image mass on his ankles extending to the foot. It was painless but affected his gait and footwear. Staged complete resection was done first on the right then on the left side, with no recurrence after 1 year. The role of genes can be argued for this presentation and giant cell tumor's etiology, owing to the bilateralism and mirror-image presentation. Studies are needed to explore this genetic aspect and its role in management.