Department of Anatomic Pathology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
Hum Pathol. 2013 Dec;44(12):2845-8. doi: 10.1016/j.humpath.2013.05.021. Epub 2013 Sep 2.
Malignant peripheral nerve sheath tumor is a malignant tumor showing nerve sheath differentiation. Approximately one-half of malignant peripheral nerve sheath tumors arise from a benign peripheral nerve sheath tumor, which is commonly a neurofibroma in patients with neurofibromatosis type 1. Malignant peripheral nerve sheath tumor arising in a sporadic schwannoma of soft tissue is extremely rare. In this condition, malignant cells usually show epithelioid morphology, meeting the diagnostic criteria for epithelioid malignant peripheral nerve sheath tumor. Here, we present an extraordinary case of spindle cell-type malignant peripheral nerve sheath tumor arising in a schwannoma on the back of a 58-year-old woman without neurofibromatosis. The malignant component showed hypercellular spindle cell proliferation with high mitotic activities; in contrast, the benign component showed hypocellular spindle cell proliferation in a palisading pattern and with Verocay bodies. Immunohistochemical S-100 protein staining showed a clear contrast between the malignant (negative) and benign (positive) components, which was useful for differentiating cellular schwannoma. Recognizing this rare condition is helpful in the pathologic diagnosis of schwannoma showing cellular proliferation in part.
恶性外周神经鞘瘤是一种表现出神经鞘分化的恶性肿瘤。大约一半的恶性外周神经鞘瘤起源于良性外周神经鞘瘤，在 1 型神经纤维瘤病患者中通常为神经纤维瘤。在散发性软组织 schwann 瘤中发生的恶性外周神经鞘瘤极为罕见。在这种情况下，恶性细胞通常呈上皮样形态，符合上皮样恶性外周神经鞘瘤的诊断标准。在此，我们报告了一例 58 岁女性背部 schwann 瘤中发生的梭形细胞型恶性外周神经鞘瘤的特殊病例，该患者无神经纤维瘤病。恶性成分表现为高有丝分裂活性的细胞丰富性梭形细胞增殖；相比之下，良性成分表现为栅栏状稀疏性梭形细胞增殖和 Verocay 小体。免疫组化 S-100 蛋白染色显示恶性（阴性）和良性（阳性）成分之间的明显对比，有助于鉴别细胞 schwann 瘤。认识到这种罕见情况有助于部分细胞增殖 schwann 瘤的病理诊断。
