滑脂肉瘤（MLS）是一种常见的脂肪肉瘤类型。它的特点是在粘液样基质中，有着不规则脂肪生成的细胞和星状毛细血管与DDIT3融合。核染色体的均一性是规律的，即使在高级圆细胞样例中也能保持。在这个研究中，我们对四个显示核异型性的MLS肿瘤进行了深入调查，这三个患者的病例占了142个MLS患者的2.1%。所有患者年龄分别为26岁、33岁和49岁，并且全都为男性。核异型性在一个患者的初发和转移性肿瘤中观察到，在另一个患者的初发肿瘤中观察到，在另一个患者的转移性肿瘤中观察到。三个肿瘤的异型性严重，一个肿瘤的异型性中等。两个肿瘤的组织学类似于分化为不同种类的脂肪肉瘤，带有粘液特征的多形性脂肪肉瘤，或多形性粘液脂肪肉瘤，一个肿瘤的组织学类似于具有局部软骨和横纹肌样分化的多形态肉瘤，还有一个肿瘤的组织学类似于上皮样多形性脂肪肉瘤。所有肿瘤都携带了FUS-DDIT3融合，并且免疫组化检测中DDIT3呈阳性。所有肿瘤都有TP53突变，而之前从同一患者提取的具有均一细胞学特征的标本中缺乏TP53突变。一个肿瘤显示出RB1缺失和完全丧失Rb表达，不能用基于DNA甲基化的方法进行分类。MLS中核异型性的罕见发生是被低估的，增加了脂肪肉瘤的诊断复杂性。即使存在核异型性，也应该对DDIT3进行广泛考虑以进行脂肪肉瘤评估。 © 2023. 作者，独家授权给施普林格-威尔斯坦德出版集团德国公司（Springer Verlag GmbH Germany），施普林格-威尔斯坦德出版集团的一部分。

Myxoid liposarcoma (MLS) is a common type of liposarcoma. It is characterized by variably lipogenic uniform cells in myxoid stroma with arborizing capillaries and DDIT3 fusion. Nuclear uniformity is the rule, which is maintained even in high-grade round cell examples. In this study, we conducted an in-depth investigation of four MLS tumors that demonstrated nuclear pleomorphism in three patients. These cases accounted for 2.1% of 142 patients with MLS. All patients were male aged 26, 33, and 49 years. Nuclear pleomorphism was observed in both primary and metastatic tumors in one patient, a primary tumor in one patient, and a metastatic tumor in another patient. Pleomorphism was severe in three tumors and moderate in one. Histology resembled that of dedifferentiated liposarcoma with myxoid features, pleomorphic liposarcoma with myxoid features, or myxoid pleomorphic liposarcoma in two tumors, pleomorphic sarcoma with focal cartilaginous and rhabdomyoblastic differentiation in one tumor, and epithelioid pleomorphic liposarcoma in one tumor. All tumors harbored FUS::DDIT3 fusions and immunohistochemically expressed DDIT3. All tumors had TP53 mutations, whereas previous specimens with uniform cytology from the same patients lacked TP53 mutations. One tumor showed RB1 deletion and complete loss of Rb expression, which was unclassifiable using DNA methylation-based methods. The rare occurrence of nuclear pleomorphism is underrecognized in MLS and increases the complexity to the diagnosis of liposarcoma. DDIT3 evaluation can be liberally considered in liposarcoma assessment even in the presence of nuclear pleomorphism.© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.