Swanson P E, Wick M R, Dehner L P
Department of Pathology, Washington University School of Medicine, St. Louis, MO.
Hum Pathol. 1991 Jun;22(6):569-77. doi: 10.1016/0046-8177(91)90234-g.
Leiomyosarcoma (LMS) of soft tissue is a rare tumor in children. Although LMS may exhibit clinical and histologic features that are typical of smooth muscle neoplasms in adults, they may often be confused with or resemble tumors of presumed fibroblastic, myofibroblastic, or rhabdomyoblastic differentiation. As a result, the diagnosis of LMS in children is often difficult to establish with confidence. To address this problem, we analyzed the immunohistochemical features of six LMS in children (one of deep soft tissue of an extremity, one of paravertebral tissue, one of the retroperitoneum, two of oropharyngeal soft tissue, and one of subcutis); the ultrastructural features of four of these tumors were also studied. Histologically, each of the three tumors of deep soft tissue and one of the retromolar trigone were composed of pleomorphic spindle cells arranged in interweaving fascicles. In contrast, the subcutaneous tumor and the lesion of the hard palate had an epithelioid appearance. Ultrastructural features were typical of adult type LMS. Immunohistochemically, these neoplasms were diffusely reactive for vimentin, while each was negative for cytokeratin, epithelial membrane antigen, and S-100 protein. Desmin was present in all cases, but was expressed only focally in three; a similar pattern of staining was noted for muscle-specific actin, although staining was generally noted in a larger population of cells. alpha-1-Antichymotrypsin was found in five tumors, and cathepsin B reactivity was encountered in four cases. Leu-7 antigen and myelin basic protein were coexpressed by one tumor, but neither was found in the remaining cases. These results indicate that immunohistochemical detection of desmin and muscle-specific actin may be useful in the differential diagnosis of spindle or epithelioid cell proliferations in childhood when ultrastructural analysis in unavailable.
软组织平滑肌肉瘤（LMS）在儿童中是一种罕见肿瘤。尽管LMS可能表现出与成人平滑肌瘤典型的临床和组织学特征，但它们常与推测为成纤维细胞、肌成纤维细胞或横纹肌母细胞分化的肿瘤相混淆或相似。因此，儿童LMS的诊断往往难以确切确立。为解决这一问题，我们分析了6例儿童LMS的免疫组化特征（1例位于肢体深部软组织，1例位于椎旁组织，1例位于腹膜后，2例位于口咽软组织，1例位于皮下）；还研究了其中4例肿瘤的超微结构特征。组织学上，3例深部软组织肿瘤和1例磨牙后三角区肿瘤均由多形性梭形细胞组成，呈交织束状排列。相比之下，皮下肿瘤和硬腭病变呈上皮样外观。超微结构特征为成人型LMS的典型表现。免疫组化方面，这些肿瘤对波形蛋白呈弥漫性反应，而对细胞角蛋白、上皮膜抗原和S - 100蛋白均为阴性。所有病例中均存在结蛋白，但仅3例呈局灶性表达；肌特异性肌动蛋白染色模式相似，尽管通常在更多细胞群体中可见染色。5例肿瘤中发现α - 1 - 抗糜蛋白酶，4例出现组织蛋白酶B反应性。1例肿瘤同时表达Leu - 7抗原和髓磷脂碱性蛋白，其余病例均未发现。这些结果表明，在无法进行超微结构分析时，免疫组化检测结蛋白和肌特异性肌动蛋白可能有助于儿童期梭形或上皮样细胞增殖的鉴别诊断。
