[Localized tenosynovial giant cell tumor of the knee. Case report]

tenosynovial giant cell tumor (TGCT) is a rare benign neoplastic condition affecting joint synovia, bursae, and tendon sheaths. It is classified as localized or diffuse based on clinical and biological behavior. Localized forms often affect small joints like fingers (85%), while diffuse forms primarily involve large joints, particularly the knee. Diffuse forms are more aggressive and can exceptionally exhibit malignancy.

a 27-year-old male presented with a 2-year history of intermittent knee locking and reduced mobility, worsening after a sports-related trauma. MRI showed hyperintense nodular lesions in the posterior capsule of the knee. Arthroscopy confirmed a mass adherent to the posterior capsule, which was excised and pathologically diagnosed as localized TGCT. The patient was discharged home without complications 24 hours' post-surgery, and a 6-month follow-up MRI showed no significant findings. Currently, the patient has full range of motion and no limitations in physical activity.

TGCT diagnosis can be challenging due to variable presentation and nonspecific symptoms, often mimicking meniscal tears. MRI is crucial for diagnosis and surgical planning. Localized forms are managed with arthroscopic excision, yielding low recurrence rates (0-10%) and excellent outcomes. Diffuse forms may require adjuvant radiotherapy or pharmacological treatments in refractory cases.