Extraskeletal myxoid chondrosarcoma: Clinicopathological features and outcomes from the United States sarcoma collaborative database

<jats:title>Abstract</jats:title><jats:sec><jats:title>Backgrounds and Objectives</jats:title><jats:p>This investigation described clinicopathological features and outcomes of extraskeletal myxoid chondrosarcoma (EMC) patients.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>EMC patients were identified from the United States Sarcoma Collaborative database between 2000 and 2016. Overall survival (OS) and recurrence‐free survival (RFS) were calculated, and prognostic factors were analyzed.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Sixty individuals with a mean age of 55 years were included, and 65.0% (<jats:italic>n</jats:italic> = 39) were male. 73.3% (<jats:italic>n</jats:italic> = 44) had a primary tumor. A total of 41.6% (<jats:italic>n</jats:italic> = 25) developed tumor relapse following resection. The locoregional recurrence rate was 30.0% (<jats:italic>n</jats:italic> = 18/60), and mean follow‐up was 42.7 months. The 5‐year OS was 71.0%, while the 5‐year RFS was 41.4%. On multivariate analysis for all EMC, chemotherapy (hazard ratio [HR], 6.054; 95% confidence interval [CI], 1.33−27.7; <jats:italic>p</jats:italic> = 0.020) and radiation (HR, 5.07, 95% CI, 1.3−20.1; <jats:italic>p</jats:italic> = 0.021) were independently predictive of a worse RFS. Among patients with primary EMC only, the 5‐year OS was 85.3%, with a 30.0% (<jats:italic>n</jats:italic> = 12) locoregional recurrence rate, though no significant prognostic factors were identified.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>Long‐term survival with EMC is probable, however there exists a high incidence of locoregional recurrence. While chemotherapy and radiation were associated with a worse RFS, these findings were likely confounded by recurrent disease as significance was lost in the primary EMC‐only subset.</jats:p></jats:sec>