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The lesion was surrounded by a split-fat sign\/fatty rind which is a typical feature of peripheral nerve sheath tumours or other benign intramuscular tumours. However, percutaneous biopsy showed MCS. We highlight how perilesional fat is not exclusive to benign intramuscular lesions and, although much less common, can be associated with malignant lesions. This is, to the best of our knowledge, the first reported case of MCS presenting with a split-fat sign at MRI.<\/jats:p>","DOI":"10.1136\/bcr-2024-261103","type":"journal-article","created":{"date-parts":[[2024,7,29]],"date-time":"2024-07-29T12:55:48Z","timestamp":1722257748000},"page":"e261103","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":1,"title":["Intramuscular mesenchymal chondrosarcoma surrounded by a split fat sign mimicking a benign lesion"],"prefix":"10.1136","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0009-0000-2463-2641","authenticated-orcid":false,"given":"Dmitriy","family":"Starostin","sequence":"first","affiliation":[{"name":"Radiology, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Samuel","family":"Crompton","sequence":"additional","affiliation":[{"name":"Radiology, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Malee","family":"Fernando","sequence":"additional","affiliation":[{"name":"Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nikhil","family":"Kotnis","sequence":"additional","affiliation":[{"name":"Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"239","published-online":{"date-parts":[[2024,7,29]]},"reference":[{"key":"2025082623150934000_17.7.e261103.1","unstructured":"WHO classification of tumours editorial board . 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