Anaplastic meningiomas can have a sarcomatous appearance on histology but true sarcomatous (metaplastic) differentiation is rare. These tumors follow an aggressive clinical course with recurrence and poor clinical outcomes. Due to significant overlap in morphology and immunohistochemical profiles, distinguishing between sarcomatous transformation of a meningioma and a true sarcoma can be challenging. Here, we outline potential diagnostic pitfalls and the utility of ancillary molecular testing in 3 patients diagnosed with sarcomatous meningiomas. We report loss of typical meningothelial markers in sarcomatous meningiomas. Ancillary molecular testing can support the diagnosis of sarcomatous meningioma when a molecular signature consistent with meningioma is seen, such as inactivation of the NF2 gene. Recognition of this rare transformation in meningioma can prevent a misdiagnosis of a primary sarcoma, whether sporadic or radiation-induced from prior treatment of a more classic meningioma.

中文翻译：

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肉瘤性脑膜瘤：诊断陷阱和分子检测的效用

间变性脑膜瘤在组织学上可呈肉瘤样表现，但真正的肉瘤（化生）分化很少见。这些肿瘤遵循具有复发性和不良临床结果的侵袭性临床过程。由于形态学和免疫组织化学特征的显着重叠，区分脑膜瘤的肉瘤转化和真正的肉瘤可能具有挑战性。在这里，我们概述了 3 名诊断为肉瘤性脑膜瘤的患者的潜在诊断缺陷和辅助分子检测的效用。我们报告了肉瘤性脑膜瘤中典型脑膜上皮标志物的丢失。当观察到与脑膜瘤一致的分子特征时，辅助分子检测可以支持肉瘤性脑膜瘤的诊断，例如 NF2 基因的失活。