A novel molecular subset of epithelioid leiomyosarcomas with rhabdoid features harboring PGR gene rearrangements has recently been documented. Herein, we present a unique case of PGR-rearranged smooth muscle tumor with both PGR-NR4A3 and UBR5-PGR gene fusions reported in a 30-year-old woman who had a mass in the broad ligament. The histological examination showed a round/polygonal to spindle cell tumor with abundant myxoid matrix and focal hyalinization, resulting in an epithelioid pattern. Immunohistochemical examination revealed that the tumor had variable staining for desmin, SMA, and h-caldesmon and diffuse nuclear staining of ER, PR, and WT1. Furthermore, targeted RNA sequencing analysis revealed PGR-NR4A3 and UBR5-PGR gene fusions. Our case in addition with the reported cases suggest that myxoid matrix with two types of tumor cells (round/polygonal epithelioid cells and spindle cells) may be significant for the diagnosis of PGR-NR4A3 fusion-positive leiomyosarcoma. UBR5-PGR gene fusion is a novel finding in epithelioid leiomyosarcoma.

最近记录了一种具有横纹肌样特征的上皮样平滑肌肉瘤的新型分子亚群，其中包含PGR基因重排。在此，我们介绍了一个独特的PGR重排平滑肌肿瘤病例，在一名 30 岁的阔韧带肿块的女性中报道了PGR-NR4A3和UBR5-PGR基因融合。组织学检查显示圆形/多边形至梭形细胞肿瘤，具有丰富的粘液样基质和局灶性透明化，导致上皮样模式。免疫组织化学检查显示肿瘤对结蛋白、SMA 和 h-caldesmon 有不同的染色，对 ER、PR 和 WT1 有弥漫性核染色。此外，靶向 RNA 测序分析揭示了PGR-NR4A3和UBR5-PGR基因融合。我们的病例以及报道的病例表明，含有两种肿瘤细胞（圆形/多边形上皮样细胞和梭形细胞）的粘液样基质可能对PGR-NR4A3融合阳性平滑肌肉瘤的诊断具有重要意义。UBR5-PGR基因融合是上皮样平滑肌肉瘤的新发现。