Bilateral Localized-Tenosynovial Giant Cell Tumor of the Knee: Case Report and Review

Background/Objectives: Tenosynovial giant cell tumor (TGCT), formerly known as pigmented villonodular tenosynovitis (PVNS), is a rare, benign, inflammatory mesenchymal neoplasm originating from the synovium of joints, bursae, or tendon sheaths. Although TGCT can affect any joint, the knee is the most commonly involved site, particularly in cases of diffuse-type TGCT. Bifocal or multifocal involvement is exceedingly uncommon. Methods: Herein, we present a case of localized TGCT with bilateral knee involvement in a 48-year-old female. Results: The patient underwent open arthrotomy with marginal excision of the localized lesions in both knees. Histology and immunohistochemistry staining conformed the diagnosis. At the five-year follow-up, the patient remains asymptomatic and free of recurrence. Conclusions: Given the rarity of bilateral TGCT, clinicians should maintain a high index of suspicion when evaluating patients presenting with bilateral knee pain and swelling and include TGCT in the differential diagnosis. To our knowledge, this represents the fifteenth reported case of bilateral knee TGCT in the literature.