Primary synovial sarcoma of bone: a retrospective analysis of 25 patients.

Histopathology 2022 Mar

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To evaluate the diagnostic accuracy of SSX and SSX::SS18 antibodies in decalcified surgical specimens and outcome of synovial sarcomas (SS) of bone. Twenty-five cases were classified as bone SS (prevalence 0.32% among malignant primary bone sarcoma). Median age was 34 years (range = 9-79). Twenty-four of 25 patients presented with non-metastatic tumours, one with lung metastases. The majority of tumours involved the long bones of extremities with metaphyseal origin. Mean size of the tumour was 7.1 cm. Twenty cases (80%) were monophasic and five (20%) were biphasic. SS18::SSX fusion-specific antibody had 92% sensitivity and 99% specificity for primary bone SS, whereas SSX C-terminus antibody had 100% sensitivity and 94% specificity. Fluorescence in-situ hybridisation (FISH) analysis was feasible in nine (36%) cases and detected SS18 rearrangement in all nine cases. All patients underwent surgical removal of their primary tumour, with adequate margins in 18 (72%) patients. Chemotherapy with metothrexate, cisplatin, doxorubicin and ifosfamide was used in the seven patients. Two patients with inadequate surgical margins received radiotherapy. With a median follow-up of 80 months (range = 6-428), 5- and 10-year overall survival (OS) was 66.6% and 47.9%, respectively, and 5 and 10 years' disease-free survival (DFS) was 36.8% [95% confidence interval (CI) = 18.0-55.7%] and 32.2% (95% CI = 14.6-51.2%), respectively. A significant improvement in 10 years' DFS in patients undergoing chemotherapy compared with patients who did not was observed (P = 0.039). Our series highlights the utility of SS18::SSX fusion-specific and SSX C-terminus antibodies to support the diagnosis of SS. Adjustment chemotherapy was associated with improved prognosis in this series. © 2021 John Wiley & Sons Ltd.

Citation

Alberto Righi, Marco Gambarotti, Stefania Benini, Dino Gibertoni, Sofia Asioli, Giovanna Magagnoli, Gabriella Gamberi, Marta Sbaraglia, Stefania Cocchi, Eric Staals, Emanuela Palmerini, Angelo Paolo Dei Tos. Primary synovial sarcoma of bone: a retrospective analysis of 25 patients. Histopathology. 2022 Mar;80(4):686-697