Benign, Aggressive, and Malignant Tenosynovial Giant Cell Tumor: Demographic, Clinical, and Imaging Characteristics of a Large Monocentric Cohort

Purpose or Learning Objective: Tenosynovial giant cell tumor (TGCT) is a common soft tissue tumor that originates in synovial cells of joints, bursae, or tendon sheaths. It is subdivided into a localized and a diffuse type based on morphology and growth pattern. Although both types share similar histologic features, cross-sectional imaging allows a precise distinction between them. Clinical presentation and risk of local recurrence differ sharply. Few cases of malignant transformation have been published to date. Therefore, radiologic assessment is essential for planning treatment strategy and evaluation of the disease course. Histologic criteria for malignant transformation include sheets and nodules of enlarged mononuclear cells with enlarged nuclei with nucleoli, spindling of mononucleated cells, increased mitotic activity, necrosis, and a reduced number of hemosiderophages. Radiologic predictor of tumor aggressiveness and malignant transformation is limited. Methods or Background: We retrospectively analyzed data of all patients with the diagnosis of TGCT who were treated at our hospital from January 1, 2007, to September 30, 2021. Our aim was to gain information on the prevalence of tumor recurrence and malignant transformation. Moreover, we hoped to identify a radiologic correlate for the histologic malignancy criteria. Results or Findings: A total of 221 patients with histologically proven TGCT were identified. The localized type (L-TCGT) was more common than the diffuse type (D-TCGT; 64% versus 36%). We observed a total recurrence rate of 15.5% (in 30.8% of D-TCGT and 8.9% of L-TCGT). There was one incidence of a locally aggressive D-TGCT affecting the hip in a 17-year-old young woman with lymphatic vessel infiltration. Moreover, one case of secondary malignant TCGT was identified (1/221 [0.5%]). We could not detect any specific changes in MR signal intensity that indicated aggressiveness or malignant transformation. However, intra-articular D-TCGT was more prone to aggressive behavior and local recurrence when compared with other morphological subtypes. Conclusion: TGCTs are predominantly benign soft tissue tumors with a low risk of malignant transformation. Diffuse intra-articular TCGT shows the highest rates of local recurrence and malignant transformation when compared with other morphological subtypes. Publication History Article published online: 02 June 2022 © 2022. Thieme. All rights reserved. Thieme Medical Publishers, Inc. 333 Seventh Avenue, 18th Floor, New York, NY 10001, USA