{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T09:47:19Z","timestamp":1782726439183,"version":"3.54.5"},"reference-count":11,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T00:00:00Z","timestamp":1782691200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Diagnostics"],"abstract":"<jats:p>A 54-year-old female patient presented with a gradually enlarging mass on the ulnar side of the left wrist. Magnetic resonance imaging demonstrated a fat-containing lesion deep within the flexor carpi ulnaris that showed heterogeneous signal intensity, as well as weak internal and peripheral enhancement, which are not typical for atypical spindle cell\/pleomorphic lipomatous tumors (ASPLTs). The imaging appearance overlapped with spindle cell lipoma (SCL), atypical lipomatous tumor\/well-differentiated liposarcoma (ALT\/WDL), and hibernoma, which made preoperative diagnosis challenging. The mass was excised en bloc. Histologically, the tumor consisted of mature adipocytes with substantial size variation, mild atypical spindle cells within a myxoid stroma, and scattered lipoblasts. Immunohistochemistry showed CD34 positivity and loss of RB1, while MDM2 amplification was absent on fluorescence in situ hybridization analysis, supporting a diagnosis of ASPLT. ASPLT is known for its broad range of morphological and radiological presentations, and this case further highlights the difficulty inherent in distinguishing it from SCL and ALT\/WDL based on imaging alone. Recognition of its diverse features and the use of molecular testing are essential for accurately diagnosing ASPLT. Surgical excision remains the standard treatment. Although recurrence has been reported, metastasis of ASPLT is exceedingly rare.<\/jats:p>","DOI":"10.3390\/diagnostics16132028","type":"journal-article","created":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T08:45:20Z","timestamp":1782722720000},"page":"2028","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Atypical Spindle Cell\/Pleomorphic Lipomatous Tumor with Atypical Imaging Features"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9850-6047","authenticated-orcid":false,"given":"Jiro","family":"Ichikawa","sequence":"first","affiliation":[{"name":"Department of Orthopaedic Surgery, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo 409-3898, Yamanashi, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1629-2549","authenticated-orcid":false,"given":"Tomonori","family":"Kawasaki","sequence":"additional","affiliation":[{"name":"Department of Pathology, Saitama Medical University International Medical Center, Hidaka 350-1298, Saitama, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kojiro","family":"Onohara","sequence":"additional","affiliation":[{"name":"Department of Diagnostic Radiology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo 409-3898, Yamanashi, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Masanori","family":"Wako","sequence":"additional","affiliation":[{"name":"Department of Orthopaedic Surgery, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo 409-3898, Yamanashi, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rikito","family":"Tatsuno","sequence":"additional","affiliation":[{"name":"Department of Orthopaedic Surgery, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo 409-3898, Yamanashi, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Taro","family":"Fujimaki","sequence":"additional","affiliation":[{"name":"Department of Orthopaedic Surgery, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo 409-3898, Yamanashi, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kouhei","family":"Mitsui","sequence":"additional","affiliation":[{"name":"Department of Orthopaedic Surgery, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo 409-3898, Yamanashi, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-5353-4477","authenticated-orcid":false,"given":"Tetsuhiro","family":"Hagino","sequence":"additional","affiliation":[{"name":"Department of Orthopaedic Surgery, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo 409-3898, Yamanashi, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5630-9600","authenticated-orcid":false,"given":"Hirotaka","family":"Haro","sequence":"additional","affiliation":[{"name":"Department of Orthopaedic Surgery, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo 409-3898, Yamanashi, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"5729","DOI":"10.21873\/anticanres.16779","article-title":"Indolent Multinodular Synovial Sarcoma of Peripheral Nerves Mimicking Schwannoma: A Case Report and Literature Review","volume":"43","author":"Kawasaki","year":"2023","journal-title":"Anticancer Res."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Creytens, D., and Marino-Enriquez, A. (2020). Atypical spindle cell\/pleomorphic lipomatous tumor. Soft Tissue and Bone Tumours, IARC Press. [5th ed.]. WHO Classification of Tumours Editorial Board.","DOI":"10.1111\/cup.13731"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"11549","DOI":"10.21037\/qims-2025-453","article-title":"Characteristic magnetic resonance imaging features of atypical spindle cell\/pleomorphic lipomatous tumor","volume":"15","author":"Onohara","year":"2025","journal-title":"Quant. Imaging Med. Surg."},{"key":"ref_4","first-page":"769","article-title":"Atypical spindle cell\/pleomorphic lipomatous tumor","volume":"35","author":"Lecoutere","year":"2020","journal-title":"Histol. Histopathol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"396.e315","DOI":"10.1016\/j.crad.2019.11.020","article-title":"Imaging of spindle cell lipoma","volume":"75","author":"Jelinek","year":"2020","journal-title":"Clin. Radiol."},{"key":"ref_6","first-page":"20170067","article-title":"Hibernoma: A rare benign soft tissue tumour resembling liposarcoma","volume":"4","author":"Kovitwanichkanont","year":"2018","journal-title":"BJR Case Rep."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"20220743","DOI":"10.1259\/bjr.20220743","article-title":"Differences in MRI findings of superficial spindle cell lipoma and atypical lipomatous tumor\/well-differentiated liposarcoma","volume":"96","author":"Kawaguchi","year":"2023","journal-title":"Br. J. Radiol."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Ichikawa, J., Kawasaki, T., Imada, H., Kanno, S., Taniguchi, N., Ashizawa, T., and Haro, H. (2022). Case report: Atypical spindle cell\/pleomorphic lipomatous tumor masquerading as a myxoid liposarcoma or intramuscular myxoma. Front. 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