[Localized tenosynovial giant cell tumor : Results from the Histopathological Arthritis Register of the German Society for Orthopedic Rheumatology].

BACKGROUND:The tenosynovial giant cell tumor (pigmented villonodular synovitis) is a proliferative, mainly benign soft tissue tumor of the tendon sheaths, bursae and joints arising from the synovia. It can be divided into circumscribed localized and destructive diffuse types. Approximately 1% of all joint diseases are due to this entity. The tumor is considered as a rarity. Mostly case studies exist. For this study the focus was set on the localized type (L-TSRZT), which accounts for 90% of the diagnoses of this tumor. Given its rarity, data are limited. Therefore, the research aim was to provide data on prevalence, primary location and sensitivity of clinical versus histopathological diagnosis in a German sample. METHODS:Based on the Histopathological Arthritis Register of the German Society for Orthopedic Rheumatology, the data of the L‑TSRZT were retrospectively analyzed (time frame 1 January 2018-28 December 2020). RESULTS:This database contained N = 7595 cases of arthropathy. A total of n = 45 patients with the diagnosis L‑TSRZT were identified. The prevalence of the tumor was 0.6%, 95% CI [0.4%, 0.8%], or 5.9 cases per 1000. The primary location involved the finger (48.9%). In 14 of 45 cases the diagnosis was correctly determined from the clinical side, corresponding to a sensitivity of 31.1%, 95% CI [18.2%, 46.7%]. CONCLUSION:For the first time, this paper was able to provide data on a large sample for Germany. Notably, the low sensitivity of the clinical diagnosis confirms the importance of histopathology for diagnosing L‑TSRZT.