Extraskeletal Myxoid Chondrosarcoma with Molecularly Confirmed Diagnosis: A Multicenter Retrospective Study Within the Italian Sarcoma Group

Background: Extraskeletal myxoid chondrosarcoma (EMC) is a rare sarcoma of uncertain origin, marked by specific chromosomal translocations involving the NR4A3 gene, and usually characterized by an indolent course. Surgery (with or without radiotherapy) is the treatment of choice in localized disease. The treatment for advanced disease remains uncertain. In order to better evaluate prognostic factors and outcome, a retrospective pooled analysis of patients with EMC treated at three Italian Sarcoma Group (ISG) referral centers was carried out. Methods: All patients with localized EMC surgically treated from 1989 to 2016 were identified. Diagnosis was centrally reviewed according to WHO 2013. Only patients with NR4A3 rearrangement were included. Results: Sixty-seven patients were identified: 13 (20%) female, 54 (80%) male. Median age was 56 years (range 18–84). Numbers and type of translocation were: 50 (80%) NR4A3-EWS, 10 (16%) NR4A3-TAF15, 1 (2%) NR4A3-TCF12, and 1 (2%) NR4A3-TFG. Median follow-up was 55 months (range 2–312). Five- and ten-year overall survival rates were 94% (86–100 95%CI) and 84% (69–98 95%CI). Thirty-five (52%) patients relapsed: 9 had local recurrence (LR) and 26 had distant metastasis (5 with concomitant LR). The 5- and 10-year disease-free survival rates (DFS) were 51% (38–65 95%CI) and 20% (7–33 95%CI). Size of the primary tumor was significantly related to distant metastasis-free survival (DMFS) (p = 0.004). Patients carrying the NR4A3-EWS translocation had a trend in favor of better DFS (p = 0.08) and DMFS (p = 0.09) compared with the patients with NR4A3-TAF15. Conclusions: Prolonged survival can be expected in patients with EMC, in spite of a high rate of recurrence. Size is significantly associated with distant relapse. The type of NR4A3 translocation could influence outcome.