Infantile fibrosarcoma: magnetic resonance imaging findings in six cases.

PURPOSE: To retrospectively review magnetic resonance (MR) imaging features in a series of six infantile fibrosarcomas to find out if MR can suggest this unusual diagnosis and to highlight the value of MR during and following treatment.

MATERIALS AND METHODS: The records of six cases of histologically proven infantile fibrosarcoma were retrieved from the files of our cancer center. All imaging data available were consensually reviewed by two radiologists.

RESULTS: There were five females and one male (age range at diagnosis, 0-12 months; mean, 6 months). The most common finding was a well-circumscribed single mass in five patients (83%). All tumors had arisen on limbs; at their proximal or distal extremity or at the root of the limb. The masses were 9 cm large in mean diameter. The initial tumor signal was isointense to muscle on T1-weighted and hyperintense on T2-weighted sequences. All masses were well circumscribed and half of them contained internal fibrous septa. The internal signal was homogeneous in three patients and heterogeneous in the three others. An intense enhancement was seen in all three contrast-enhanced exams available; heterogeneous in two cases and homogeneous in one. Osseous erosion was observed in only one patient who was the only one with distant metastasis. After treatment (chemotherapy and very limited surgery), tumors had totally disappeared, leaving muscle fat infiltration in two patients and subcutaneous fat hypertrophy in one patient.

CONCLUSION: Although imaging findings are not specific of infantile fibrosarcoma, this diagnosis could be suggested when MR imaging depicts a large well-circumscribed mass arising in a limb at birth or during the neonatal period. This mass is sometimes heterogeneous and septate and exhibits an isointense T1- and hyperintense T2-weighted signals and strong enhancement. MR is also the technique of choice for follow-up during treatment which consists nowadays almost exclusively in chemotherapy.