MR imaging of myxofibrosarcoma and undifferentiated sarcoma with emphasis on tail sign; diagnostic and prognostic value.

OBJECTIVES

To assess the prevalence of the tail sign in soft tissue sarcomas and determine whether the local recurrence rate differed based on the presence of the tail sign.

METHODS

In our retrospective study, myxofibrosarcoma (MFS, n = 25) and undifferentiated sarcoma (US, n = 38) comprised group 1, and the remaining tumours (n = 115) were assigned to group 2. Location, size, and imaging features of the tumours were assessed on MRI. The radiological-pathological correlation of the tail sign was analysed.

RESULTS

The tail sign, thick fascial enhancement extending from the tumour margin, was more common and significantly thicker in group 1. In the subgroup analysis between MFS and US, there was no significant difference in the presence of a tail sign. Histological examination revealed extensive tumour cell infiltrations along the deep fascia from the main mass. Patients with a tail sign had a worse local recurrence-free survival than patients without it, not only in all tumours (p < 0.01), but also in group 1 (p = 0.019) CONCLUSIONS: The tail sign was a common MRI feature of both MFS and US, and was also associated with worse local recurrence-free survival. Radiologists should be aware of these MRI findings and inform the surgeon preoperatively in order to obtain a sufficient surgical margin to minimise the risk of local tumour recurrence.

KEY POINTS

• The tail sign was a common MRI feature of myxofibrosarcoma and undifferentiated sarcoma. • The tail sign may be associated with worse local recurrence-free survival • Radiologists should be aware of this MRI finding and inform the surgeon.