Lee Anna F, Hayes Malcolm M, Lebrun David, Espinosa Inigo, Nielsen G Petur, Rosenberg Andrew E, Lee Cheng-Han
Department of Pathology, Vancouver General Hospital, Vancouver, British Columbia, Canada.
Appl Immunohistochem Mol Morphol. 2011 May;19(3):233-8. doi: 10.1097/PAI.0b013e3181fd6697.
Small cell osteosarcoma and mesenchymal chondrosarcoma are 2 primary bone tumors with a small round blue cell component, which can mimic the appearance of Ewing sarcoma. Distinguishing these tumors from each other on biopsy material is important clinically, as optimal therapy differs according to the tumor type. However, separating these entities on morphology alone can be challenging. FLI-1 has been described to be a useful marker for Ewing sarcoma, particularly when hematolymphoid markers are negative. In small cell osteosarcoma and mesenchymal chondrosarcoma, the FLI-1 staining pattern has not been adequately characterized. Using a monoclonal FLI-1 antibody, nuclear immunoreactivity in tumor cells was evaluated in 10 small cell osteosarcomas, 10 mesenchymal chondrosarcomas, and 8 Ewing sarcomas, together with a number of other small, round, blue cell tumors. None of the small cell osteosarcomas or mesenchymal chondrosarcomas exhibited FLI-1 staining in the tumor cells, in contrast to the positive nuclear FLI-1 staining in the stromal endothelial cells. In comparison, 6 of the 8 Ewing sarcomas showed moderate-to-strong nuclear FLI-1 staining of the tumor cells in addition to strong staining of the stromal endothelial cell nuclei. With the exception of lymphoblastic lymphomas, FLI-1 positivity was not seen in the other small round blue cell tumors examined. These findings show that, in contrast to Ewing sarcoma, small cell osteosarcoma and mesenchymal chondrosarcoma lack FLI-1 immunoreactivity. FLI-1 is therefore useful in the differential diagnosis of small round blue cell tumors of the bone.
小细胞骨肉瘤和间叶性软骨肉瘤是两种具有小圆形蓝细胞成分的原发性骨肿瘤，它们可能会模仿尤因肉瘤的外观。在活检材料上区分这些肿瘤在临床上很重要，因为最佳治疗方法因肿瘤类型而异。然而，仅靠形态学来区分这些实体可能具有挑战性。FLI-1已被描述为尤因肉瘤的一种有用标志物，特别是当血液淋巴标志物为阴性时。在小细胞骨肉瘤和间叶性软骨肉瘤中，FLI-1的染色模式尚未得到充分描述。使用单克隆FLI-1抗体，对10例小细胞骨肉瘤、10例间叶性软骨肉瘤、8例尤因肉瘤以及一些其他小圆形蓝细胞肿瘤的肿瘤细胞中的核免疫反应性进行了评估。与基质内皮细胞核中FLI-1阳性染色形成对比的是，小细胞骨肉瘤或间叶性软骨肉瘤的肿瘤细胞均未表现出FLI-1染色。相比之下，8例尤因肉瘤中有6例除了基质内皮细胞核有强染色外，肿瘤细胞还显示出中度至强的核FLI-1染色。在所检查的其他小圆形蓝细胞肿瘤中，除了淋巴母细胞淋巴瘤外，均未发现FLI-1阳性。这些发现表明，与尤因肉瘤不同，小细胞骨肉瘤和间叶性软骨肉瘤缺乏FLI-1免疫反应性。因此，FLI-1在骨小圆形蓝细胞肿瘤的鉴别诊断中很有用。
