对脱分化子宫平滑肌肉瘤（LMS）进行形态学和免疫表型鉴定。我们鉴定了23个脱分化子宫LMS，其定义为恶性子宫平滑肌瘤，包含有明确的分化和脱分化组分（即有平滑肌分化形态学和免疫表型证据的和没有的）。在大多数情况下，分化组分为平滑肌肉瘤（17/23），但有些来源于平滑肌瘤（n=4）或具有不确定恶性潜力的平滑肌肿瘤（n=2）。脱分化肿瘤组分显示出非粘着的多边形细胞，细胞质量中等到丰富，核球形多形，染色质具有粗大的泡状或污迹状，一个或多个大核仁，频繁的多核现象和非典型有丝分裂。三个病例表现出异种性骨肉瘤或软骨肉瘤分化。免疫组化揭示了子宫LMS的特征性变化，包括Rb损失（18/19）；强烈的弥漫性p16（17/19）；强烈的弥漫性（9/19）或完全缺失（5/19）p53；和ATRX损失（6/16）。与没有脱分化的子宫LMS的对照组相比，脱分化子宫LMS表现出明显较短的疾病特异性（中位数54与20个月;5年DSS，46%与36%;P=0.04）和疾病自由（中位数31与8个月;5年DFS，42%与8%;P=0.002）生存。在19个有随访的脱分化子宫LMS中，12个在中位数14个月（范围为2-73个月）内死于疾病；四个在4、12、44和50个月时仍活着，但身患疾病；而三个在56、109和114个月时仍活着，没有发现疾病的证据。提倡常规前瞻性识别脱分化子宫LMS并与模拟物区别开来，以实现准确的预后评估，并进一步表征这些肿瘤。 © 2023 The Authors.Histopathology出版John Wiley& Sons Ltd.

To morphologically and immunophenotypically characterize dedifferentiated uterine leiomyosarcoma (LMS).We identified 23 dedifferentiated uterine LMS, defined as a malignant uterine smooth muscle tumour containing discrete differentiated and dedifferentiated components (i.e. with and without morphologic and immunophenotypic evidence of smooth muscle differentiation, respectively). The differentiated component was leiomyosarcoma in most cases (17/23), though some arose from a leiomyoma (n = 4) or smooth muscle tumour of uncertain malignant potential (n = 2). The dedifferentiated tumour component showed noncohesive polygonal cells with moderate to abundant cytoplasm, pleomorphic nuclei with coarse vesicular to smudged chromatin, one or more macronucleoli, frequent multinucleation, and atypical mitoses. Three cases showed heterologous osteosarcomatous or chondrosarcomatous differentiation. Immunohistochemistry revealed alterations characteristic of uterine LMS, including Rb loss (18/19); strong diffuse p16 (17/19); strong diffuse (9/19) or complete absence of (5/19) p53; and ATRX loss (6/16). Compared to a control cohort of uterine LMS without dedifferentiation, dedifferentiated uterine LMS showed significantly shorter disease-specific (median, 54 versus 20 months; 5-year DSS, 46% versus 36%; P = 0.04) and disease-free (median, 31 versus 8 months; 5-year DFS, 42% versus 8%; P = 0.002) survival. Of 19 dedifferentiated uterine LMS with follow-up, 12 had died of disease at median 14 (range, 2-73) months; four were alive with disease at 4, 12, 44, and 50 months; and three were alive with no evidence of disease at 56, 109, and 114 months.Routine prospective recognition of dedifferentiated uterine LMS and distinction from mimics is advocated for accurate prognostication and for further characterisation of these tumours.© 2023 The Authors. Histopathology published by John Wiley & Sons Ltd.