Low-Grade Fibromyxoid Sarcoma: Incidence, Treatment Strategy of Metastases, and Clinical Significance of the FUS Gene

Abstract

Aim. The aim of this study was to assess the incidence of low-grade fibromyxoid sarcoma (LGFMS), present treatment results of metastatic LGFMS, and investigate the clinical significance of the FUS gene rearrangement. Methods. This study included 14 consecutive LGFMS patients treated at the Aarhus Sarcoma Centre in 1979-2010. Fluorescent in situ hybridization (FISH) analysis for FUS break-apart was performed for all patients. Results. The incidence of LGFMS was 0.18 per million, representing 0.6% of all soft tissue sarcomas. Four patients needed multiple biopsies/resections before the correct diagnosis was made. Four patients experienced local recurrence, and three patients developed metastases. The treatment of metastatic LGFMS varied from multiagent chemotherapy to repeated, selective surgery of operable metastases. The best response to chemotherapy was short-term stabilization of disease progression, seen with Trabectedin. The prevalence of the FUS break-apart was 21.4%. We found no significant difference in clinical characteristics and outcomes in correlation with the FUS break-apart. Conclusion. LGFMS is a rare disease with multiple challenges. The FUS break-apart was not associated with local recurrence or metastases in our study. To date the only treatment resulting in disease-free periods is surgery; however further investigation into the management of metastatic LGFMS is necessary.

Figure 1

Low-grade fibromyxoid sarcoma with (a) fibrous parts (including hints of collagenous rosettes) on the upper left and myxoid parts opposite (case 1) H&E ×100 and (b) myxoid parts with classic whorling spindle cells and curvilinear thin vessels (case 14) H&E ×200.

Figure 2

Imaging of the pelvic area in case 14. PET-CT scan showing three positive lesions on the left side: one in the pelvic area (a) and two in the thigh (b). MRI scan showing an additional lesion in the gluteal muscle on the right side (c), not positive on the PET-CT scan (d).