Ovarian small cell carcinoma of the hypercalcemic type (SCCOHT)/ovarian rhabdoid tumor is a rare and highly malignant tumor that typically occurs in young women. Up until now the diagnosis has been made on the basis of morphology without any specific immunohistochemical (IHC) markers. However, several authors have shown recently that SCCOHTs are characterized by inactivation of the SMARCA4 gene (encoding the BRG1 protein) resulting in a loss of BRG1 protein expression in IHC. We evaluated BRG1 and INI1 expression in 12 SCCOHTs and in a series of 122 tumors that could mimic SCCOHT morphologically: 9 juvenile granulosa cell tumors, 47 adult granulosa cell tumors, 33 high-grade ovarian serous carcinomas, 9 desmoplastic round cell tumors, 13 Ewing sarcomas (5 from the pelvis and 8 from soft tissues), 1 round cell sarcoma associated with CIC-DUX4 translocation from soft tissue (thigh), 1 case of high-grade endometrial stromal sarcoma of the ovary, and 9 melanomas. Forty-four adult granulosa cell tumors were interpretable by IHC. All 12 SCCOHTs were devoid of BRG1 expression and expressed INI1. All other interpretable 119 tumors showed BRG1 nuclear positivity, with variable staining proportions, ranging from 10% to 100% of positive cells (mean: 77%, median: 80%), variable intensities (weak: 5%, moderate: 37%, strong: 58%), and distributions: diffuse in 82 cases (70%) and heterogenous in 36 cases (30%). BRG1 positivity was heterogenous in desmoplastic round cell tumors and adult granulosa cell tumors. Overall, BRG1 is a useful diagnostic marker in SCCOHT, showing the absence of expression in SCCOHT. Nevertheless, the possible heterogeneity and the variable intensity of this staining warrant caution in the interpretation of BRG1 staining in biopsy specimens.
卵巢高钙血症型小细胞癌 (SCCOHT)/卵巢横纹肌样瘤是一种罕见且高度恶性的肿瘤，通常发生于年轻女性。直到现在，一直依靠形态学来诊断，没有任何特异的免疫组化(IHC)标记物。然而，近期已有几位作者证明SCCOHTs的特征是SMARCA4基因 (编码BRG1蛋白) 失活，导致IHC中BRG1蛋白失表达。我们评估了12例 SCCOHTs和形态学类似于SCCOHT的122例肿瘤中的BRG1和INI1表达，后122例肿瘤包括9例幼年型颗粒细胞瘤、47例成人型颗粒细胞瘤、33例卵巢高级别浆液性癌、9例促结缔组织增生性圆细胞肿瘤、13例尤文肉瘤 (5例来自骨盆，8例来自软组织)、1例软组织（大腿）伴CIC-DUX4易位的圆细胞肉瘤、1例卵巢高级别子宫内膜间质肉瘤及9例黑色素瘤。有44例成人型颗粒细胞瘤通过IHC判读得以证实。所有12例SCCOHTs都缺乏BRG1和INI1的表达。所有119例形态学与SCCOHTs类似且可供判读的肿瘤都显示BRG1核阳性表达，着色比例不一，阳性细胞范围10%—100%（平均：77%，中位数：80%），染色强度不一 (弱: 5%，中等: 37%， 强: 58%)，阳性分布：82例呈弥漫性 (70%) 、36例呈异质性(30%)。促结缔组织增生性圆细胞肿瘤和成人型颗粒细胞瘤的BRG1呈异质性阳性。综上所述， BRG1是诊断SCCOHT有用的标记物之一，表现为失表达。然而，活检标本中判读BRG1染色，要警惕其异质性表达的可能及其染色强度的变化。