Objective
To determine MR and CT imaging features of low grade fibromyxoid sarcoma (LGFMS) in children.
Materials and methods
We retrospectively analyzed images of 11 pediatric patients with diagnosis of LGFMS from a phase III clinical trial of non-rhabdomyosarcoma soft tissue sarcoma (Children’s Oncology Group Protocol ARST0332). MRI and CT were performed in 10 and 4 patients, respectively. Location, size, margin, and composition on imaging were correlated to pathology.
Results
Tumors were located in extremities in 9 patients and one each in tongue and lung. Tumors were deep in 7 patients and superficial in 4. All tumors were well defined, solitary, and non-metastatic at presentation. Tumors were complex solid-cystic in 8 patients and completely solid in 3. On T1W images, all tumors had at least some areas hypointense to muscles, and 6 had a “split-fat” sign. On STIR/T2W images, 8 tumors had areas hypointense to adjacent muscle and 8 tumors had fluid signal intensity. On post-contrast MR studies, 8 tumors had thick enhancing internal septations, and 3 had peripheral nodular gyriform enhancement. Correlating to pathology, areas with hypointense signal intensity on both T1 and T2W images are likely related to fibrous component; areas with fluid signal intensity on T2W images are likely related to myxoid component. On CT imaging, all 4 tumors were hypodense to muscle and one tumor showed punctate calcific foci.
Conclusion
LGFMS is hypodense to muscle on CT imaging. MR imaging may identify both fibrous and myxoid components of this rare pediatric soft tissue sarcoma.