The Extracompartmental Tumoral Invasion of Extraskeletal Myxoid Chondrosarcoma Induces Distant Metastasis.

Background: Extraskeletal myxoid chondrosarcoma (EMC) is a rare malignant soft-tissue tumor and often shows extracompartmental tumoral invasion. The aim of our study was to investigate the clinical features, especially extra-compartmental tumoral invasion (ETI) of EMC. Patients and Methods: A total of 35 operative patients diagnosed with EMC were enrolled in this study from January 1980 to March 2018 in the Cancer Institute Hospital of The Japanese Foundation for Cancer Research. The operative procedure was principally wide excision. Univariate analysis assessed how clinicopathological factors (e.g. age, gender, tumor site, tumor size, histopathological grade, surgical margin, metastasis before operation, barrier invasion, local recurrence, metastasis after operation) influenced patient prognosis. We assessed how clinicopathological factors influenced ETI of EMC. Results: Among 35 patients, 10 patients showed ETI. The average follow-up was 5.57 (range=0.2-20 years). The 5- and 10-year overall survival was 91.3% and 71.2%, respectively. The 5- and 10-year overall survival of patients with M0 disease was 96.1% and 73.2%, respectively, while both were 75.0% for those with M1 disease, respectively. The patients with distant metastasis at first visit tended to have a poor prognosis (p=0.07). It is notable that all of the 10 patients with ETI had distant metastasis after surgery. Conclusion: Patients with distant metastasis at first visit tended to have a poor prognosis. ETI of EMC induced distant metastasis after surgery. Patients with ETI of EMC should, therefore, be carefully monitored over a prolonged period.