Abstract：
ISLET-1 (ISL1) is a LIM-homeodomain transcription factor. Selective ISL1 expression is shown in neuroendocrine, non-neuroendocrine, and some soft tissue tumors including desmoplastic small round cell tumor (DSRCT). We assessed the specificity of ISL1 (clone EP283, 1:500, Cell Marque) in 288 soft tissue tumors, which included 17 DSRCTs and other histologic mimics. Positive staining threshold for ISL1 was set to >10 % of neoplastic cell nuclei at moderate intensity. ISL1 IHC was positive in 15/16 (94 %) DSRCTs with 75 % showing diffuse (>50 %) expression. ISL1 was positive in 1/10 (10 %) Ewing sarcomas (EWS), 7/13 (54 %) alveolar rhabdomyosarcoma (RMS), 14/22 (63 %) embryonal RMS, 7/14 (50 %) synovial sarcomas, 15/16 (93 %) neuroblastoma, 1/5 (20 %) Wilms tumor, 2/4 (50 %) olfactory neuroblastoma, and all 9 Merkel cell carcinomas. Other tumors, including all CIC::DUX4 sarcomas, were negative except 3/27 leiomyosarcomas, and 1 each of angiosarcoma, myxoid liposarcomas, inflammatory myofibroblastic tumor, malignant peripheral nerve sheath tumor, tenosynovial giant cell tumor, dedifferentiated LPS, and 1 ectomesenchymoma. In summary, among the soft tissue tumors tested, ISL1 is a highly sensitive but moderately specific marker for DSRCT and may be useful to distinguish from round cell mimics including EWS and CIC::DUX4 sarcomas. The oncogenic role of ISL1 in these tumors warrants further investigation.
摘要：
ISLET-1(ISL1)是LIM同源结构域转录因子。选择性ISL1表达显示在神经内分泌，非神经内分泌,和一些软组织肿瘤，包括促纤维增生性小圆细胞瘤（DSRCT）。我们评估了ISL1（克隆EP283，1:500，细胞标记）在288个软组织肿瘤中的特异性，其中包括17个DSRCT和其他组织学模拟。ISL1的阳性染色阈值设定为中等强度的>10%的肿瘤细胞核。ISLlIHC在15/16(94%)DSRCT中呈阳性,其中75%显示弥漫性(>50%)表达。ISL1在1/10（10%）尤因肉瘤（EWS）中呈阳性，7/13（54%）肺泡横纹肌肉瘤（RMS），14/22（63%）胚胎RMS，7/14（50%）滑膜肉瘤，15/16（93%）神经母细胞瘤，1/5（20%）肾母细胞瘤，2/4（50%）嗅觉神经母细胞瘤，和所有9个默克尔细胞癌。其他肿瘤,包括allCIC::DUX4肉瘤，除3/27平滑肌肉瘤外，均为阴性，各1个血管肉瘤，粘液样脂肪肉瘤，炎性肌纤维母细胞瘤，恶性周围神经鞘瘤，腱鞘巨细胞瘤，去分化LPS,和1个外胚膜瘤。总之,在测试的软组织肿瘤中，ISL1是DSRCT的高度敏感但中等特异性的标记，可用于区分圆形细胞模拟物，包括EWS和CIC::DUX4肉瘤。ISL1在这些肿瘤中的致癌作用值得进一步研究。
