# A Case Report on an Uncommon Presentation of Giant Cell Tumor of the Tendon Sheath in the Infrapatellar Region

## TL;DR

A 34-year-old woman had a rare giant cell tumor in her knee area, successfully treated with surgery and no recurrence over five years.

## Contribution

This case report highlights a rare presentation of GCT-TS in the infrapatellar region and demonstrates the effectiveness of surgical excision.

## Key findings

- The patient had a well-defined soft tissue mass in the infrapatellar region confirmed as GCT-TS.
- Surgical excision resolved symptoms and prevented recurrence over five years of follow-up.
- This case expands the known anatomical locations for GCT-TS beyond typical hand and finger sites.

## Abstract

Giant cell tumor of the tendon sheath (GCT-TS) is a benign yet locally aggressive soft tissue neoplasm that typically arises in synovium-lined structures, including tendon sheaths, bursae, and joints. Also known as localized nodular tenosynovitis, this tumor primarily affects the hands and fingers but can occur in other anatomical locations. GCT-TS is histologically characterized by multinucleated giant cells within a background of mononuclear stromal cells.

While it is generally nonmetastatic, the tumor carries a risk of local recurrence following surgical removal. Recognizing the clinical presentation, histopathological features, and appropriate management strategies is essential for effective treatment and recurrence prevention.

Here, we present the case of a 34-year-old woman with a one-year history of pain in the infrapatellar region. Imaging revealed a well-defined soft tissue mass posterior to the patellar tendon, which was surgically excised. Histopathological examination confirmed the diagnosis of nodular-type GCT-TS. The patient's symptoms resolved completely postoperatively, and no recurrence was observed during a five-year follow-up period, highlighting the effectiveness of surgical excision in managing this rare tumor location.