Uncommon Localization of Tenosynovial Giant Cell Tumor in the Coracoclavicular Ligament: Diagnostic Challenges

BACKGROUND Tenosynovial giant cell tumor (TGCT) can be characterized as localized when it occurs in the fingers and wrist, or diffuse, when it occurs in large weight-bearing joints, such as hips, knees, and ankles. However, the occurrence of TGCT in the coracoclavicular ligament is rare and has not been reported in the literature. In this case, inexperienced doctors are prone to misdiagnosis or underdiagnosis, which in turn leads to patients not being able to get the correct treatment in time. CASE REPORT This is a report of a 16-year-old female patient with symptoms of right shoulder pain and movement limitation for 1 month, aggravated for 1 week. She had received medication and physical therapy at an outside hospital, but with no improvement in her symptoms. She was admitted to our hospital and underwent tumor resection after complete imaging examination, and tissue specimens were taken for pathological examination. Pathologic results suggested TGCT. After surgery, the shoulder function gradually returned to normal. There was no sign of tumor recurrence in the right shoulder at 6 months, 1 year, and 2 years postoperatively. CONCLUSIONS This rare case shows that TGCT should be considered when a nodular lesion with equisignal in the T1-weighted image and mixed signals in the T2-weighted image is visualized on magnetic resonance imaging, and when computed tomography suggests a circumferential calcified lesion at the margin. Early diagnosis, treatment, and long-term follow-up after surgery can effectively reduce tumor expansion and recurrence risk.