Abstract: Background and purpose: Myxoid fibrosarcoma (MFS) is a rare malignant fibrogenic soft tissue tumor and more common in the elderly, which is highly invasive and prone to recurrence. At present, the diagnosis of this tumor is difficult to some extent. Imaging has a certain credibility for determining whether the soft tissue tumor is sarcoma and its malignancy, but it can only be used as a reference for the qualitative characterization of the tumor. The purpose of this study was to improve the diagnostic level of MFS by analyzing the imaging manifestations, clinical features and pathological correlation, and to further classify it into low, medium and high grade. Methods: From January 2019 to February 2021, imaging, clinical and pathological data of 11 patients with surgically proven MFS in the Fudan University Shanghai Cancer Center and 22 patients in the Minhang Branch of Fudan University Shanghai Cancer Center were collected. Imaging data was obtained through measurement of the tumor shape, size, density/signal, degree of enhancement and surrounding tissue infiltration and other signs. Clinical features included gender, age, prone site, symptoms and signs of patients. Pathology grading of Ⅰ, Ⅱ and Ⅲ were performed according to the proportion of myxoid, tumor cells and fibrous components in the sampled tissues, as well as the size of tumor cell atypia and the number of mitotic figures. Results: In this study, 5 patients had grade Ⅰ MFS, 10 patients had grade Ⅱ-Ⅲ MFS, and 18 patients had grade Ⅲ MFS. In 10 cases, the maximum diameter of the tumor was ≥5 cm. Myxoid changes were observed in 10 cases. Cystic necrosis was observed in 22 cases. Tail sign was observed in 30 cases. Double hyposignal sign was observed in 27 cases, and peritumoral edema was observed in 23 cases. There was no significant difference in the size, tail sign and double hyposignal sign among the three groups of mild, moderate and high MFS (P>0.05). There were statistically significant differences in myxoid degeneration, necrotic cystic degeneration and peritumoral edema among the three groups (P<0.05). Conclusion: Computed tomography (CT) and magnetic resonance imaging (MRI) have specific correlation with the clinical manifestations and pathological features of MFS.

Key words: Myxoid fibrosarcoma, Computed tomography, Magnetic resonance imaging, Clinical features, Pathology