Plexiform neurofibromas are an uncommon variant of neurofibromas that are described as being essentially pathognomonic of neurofibromatosis type 1 (NF1). Plexiform neurofibromas in the absence of NF1 are extremely rare. We present the case of a 38-year-old woman with a large multilobulated lumbosacral mass extending into the pelvis and proximal thigh. Histopathology of a CT-guided biopsy of the mass revealed it to be a neurofibroma. The imaging findings were consistent with a plexiform subtype. Further imaging and clinical workup showed that the patient had no other identifiable neurofibromas and did not meet criteria for the diagnosis of NF1.

中文翻译：

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腰ac丛状神经纤维瘤：罕见的成年人，没有I型神经纤维瘤病

丛状神经纤维瘤是神经纤维瘤的罕见变体，被描述为本质上是1型神经纤维瘤病（NF1）的病原学。缺乏NF1的多形神经纤维瘤极为罕见。我们提出了一个38岁的女人的病例，该人的腰s部大块状肿物延伸到骨盆和大腿近端。CT引导的肿块活检的组织病理学显示，它是神经纤维瘤。影像学发现与丛状亚型一致。进一步的影像学检查和临床检查显示，该患者没有其他可识别的神经纤维瘤，也不符合NF1诊断标准。