<qa>  What is the purpose of the study?For the evaluation of limbs soft-tissue masses, US is widely used as a first level modality. The reasons are that US is widely available, fast, easily repeatable and often more accessible than CT and MR Imaging. In addition, US equipped with high-frequency transducers have a spatial resolution that may be comparable or higher than that of MR Imaging and CT in the evaluation of superficial soft-tissues. US and MR Imaging are often not able to differentiate benign from malignant tumours, therefore several lesions detected with US or MR Imaging warrant biopsy. The clinical practice guidelines of the ESMO European Society of Medical Oncology published in 2010 found that there are no published data to indicate the optimal routine follow-up policy of surgically treated patients with localized disease. Moreover, it has not been demonstrated that, for limb sarcomas recurrences, MR Imaging is superior and cost-effective compared to US for the assessment of the primary site. Considering that surgically treated intermediate-high-grade patient may be followed frequently, even every 3-4 months in the first 2-3 years and considering that performing US is easier than having MR Imaging, the purpose of this study is to evaluate the diagnostic performance of US in the detection of local recurrences of adults patients with soft tissue sarcomas of the limb. 