The aim of the present study was to evaluate the magnetic resonance imaging (MRI) data of patients with Stewart-Treves Syndrome (STS), and to compare them with the corresponding pathological data. A total of 4,289 cases of secondary upper limb lymphedema (LE) from a single center, including 5 female cases of STS who underwent modified-radical post mastectomy, were included in the study. All cases were diagnosed pathologically, and by conventional and contrast-enhanced (ce)MRI scans. A total of 43 tumor nodules (Phi >= 4 mm) were examined. According to the immunohistochemical results, the 5 cases of STS were divided into 2 types; 4 patients exhibited STS type I [angiosarcoma (AS)] and I patient exhibited STS type 2 [mixed lymphangiosarcoma (mLAS)]. The MRI signal intensity (SI) of all the nodules was compared with the pathological results. In the T1WI sequences, all nodules showed isointensity compared with normal muscle tissues in the same image. However, in the T2WI sequences, there were the visually recognizable differences in the SI compared with the LE tissues in the two STS types. The SI of mLAS was more markedly decreased compared with that of AS. The SI of mLAS was closer to that of normal muscle tissues compared with the SI of AS. In the ceMRI, the SI of the tumor nodules was markedly increased in the two STS types, compared with non-enhancement imaging. Overall, MRI is a useful tool for the evaluation and diagnosis of STS. A chronic case of LE, in which MRI examination demonstrates nodules within the LE, may suggest a diagnosis of STS.