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Background and Objectives : Tenosynovial giant cell tumors (TSGCTs) are benign soft tissue tumors that are divided into localized- and diffuse-type tumors, according to the World Health Organization classification of soft tissue tumours. The diffuse-type TSGCT sometimes behave aggressively and poses treatment challenges especially in patients with neurovascular involvement. Symptomatic patients who are not good candidates for surgery due to high morbidity risk may benefit from medical therapy. Objectives : Drugs that target programmed death ligand 1 (PD-L1) are among a new generation of medical therapy options, which, recently, have been explored and have displayed promising results in various cancer types; therefore, we aimed to investigate the PD-L1 status of TSGCTs as a possible therapeutic target. Materials and Methods : We assessed the PD-L1 status of 20 patients (15 men and 5 women, median age = 39 years) that had been diagnosed with TSGCTs in a single institution, between 2018 and 2020. The patients had localized- ( n = 7) and diffuse-type ( n = 13) TSGCTs. Formalin-fixed paraffin-embedded (FFPE) blocks were retrospectively retrieved from the pathology department. An immunohistochemical analysis was performed in sections of 3 micron thickness from these blocks. Results : Seventy-five percent of our patients with TSGCTs were immunopositive to PD-L1 staining. Conclusions : Taking into consideration the high positivity rate of PD-L1 staining in TSGCTs, PD-L1 blockage may be used as a valuable medical treatment for TSGCTs; however, further studies are needed.

The hand is an extremely rare site for giant cell tumor (GCT). There are only a few reported cases of GCT including the hand, and even fewer reporting involvement of phalanges. GCTs in small bones are typically more aggressive and have higher local recurrence and rate of metastasis in younger patients compared to long bone involvement, so the treatment is more clinically challenging in the hand. In this study, we present the management of giant cell tumors of the proximal phalanxin two patients treated with two different method; ray resection and arthrodesis using an iliac crest graft. Key words: giant cell tumor, phalanx, hand, recurrence.