Sabater-Marco Vicente, Zapater Latorre Enrique, Martorell Cebollada Miguel
Department of Pathology, University General Hospital, Valencia, Spain.
J Cutan Pathol. 2014 Mar;41(3):316-21. doi: 10.1111/cup.12282. Epub 2014 Jan 24.
Rhabdomyosarcoma is a malignant mesenchymal neoplasm that rarely presents as primary skin tumor. So-called amianthoid fibers are hyalinized collagen mats that have been described in myofibroblastic tumors but not in rhabdomyosarcoma. A 65-year-old male developed a submandibular nodule 9 years after an oral squamous cell carcinoma, which had been treated with chemotherapy and radiotherapy. Histological examination of the nodule revealed a pleomorphic rhabdomyosarcoma with extracellular collagen deposits reminiscent of so-called amianthoid fibers. By immunohistochemistry, the tumor cells were positive for vimentin, desmin, smooth muscle actin (SMA), muscle-specific actin (MSA), CD10, CD56, CD99, β-catenin and D2-40. However, only 15-20% of the tumor cells were positive for myoglobin, MyoD1 and myf-4/myogenin. We describe first so-called amianthoid fibers harboring blood capillaries in a rhabdomyosarcoma, suggesting that they are rigid collagen structures that lead to tumor vascularization. The low expression for myogenic regulatory proteins and strong expression for other markers may be misleading and do not contribute to the diagnosis of rhabdomyosarcoma.
横纹肌肉瘤是一种恶性间叶性肿瘤，很少以原发性皮肤肿瘤的形式出现。所谓的石棉样纤维是透明变性的胶原垫，已在肌成纤维细胞肿瘤中有所描述，但在横纹肌肉瘤中未见报道。一名65岁男性在接受化疗和放疗的口腔鳞状细胞癌9年后出现下颌下结节。对该结节的组织学检查显示为多形性横纹肌肉瘤，伴有细胞外胶原沉积，让人联想到所谓的石棉样纤维。免疫组织化学检测显示，肿瘤细胞波形蛋白、结蛋白、平滑肌肌动蛋白（SMA）、肌肉特异性肌动蛋白（MSA）、CD10、CD56、CD99、β-连环蛋白和D2-40呈阳性。然而，只有15%-20%的肿瘤细胞肌红蛋白、MyoD1和myf-4/肌细胞生成素呈阳性。我们首次描述了横纹肌肉瘤中含有毛细血管的所谓石棉样纤维，提示它们是导致肿瘤血管形成的刚性胶原结构。肌源性调节蛋白的低表达和其他标志物的高表达可能会产生误导，无助于横纹肌肉瘤的诊断。
