Decoding <scp>UTROSCT</scp> heterogeneity: systematic clinicopathological evaluation combined with molecular profiling

Uterine tumor resembling ovarian sex cord tumor (UTROSCT) constitutes an exceptionally rare histological subset of uterine mesenchymal neoplasms. While most cases have benign clinical behavior, a subset of UTROSCTs exhibits clinically aggressive behavior characterized by recurrence and metastasis. Here, we present a cohort of 25 UTROSCT cases molecularly confirmed by recurrent fusion gene detection, including ESR1::NCOA3 (n = 12), GREB1::NCOA1 (n = 6), ESR1::NCOA2 (n = 3), GREB1::NCOA2 (n = 2), GREB1::SS18 (n = 1), and GREB1::CTNNB1 (n = 1). Notably, six cases (6/25, 24%) demonstrated recurrence/metastasis: two cases showed intrauterine recurrence (harboring ESR1::NCOA3 and GREB1::NCOA1 fusions), while four developed extrauterine metastases (carrying ESR1::NCOA3, ESR1::NCOA2, GREB1::NCOA1, and GREB1::NCOA2 fusions), with one fatality. To dissect the biological basis of UTROSCT aggressiveness, we performed integrated clinicopathologic, immunohistochemical, and molecular profiling. Multivariate analysis identified tumor size >5 cm, FIGO stage IB, and lymphovascular space invasion (LVSI) as independent predictors of recurrence/metastasis, whereas histologic features, proliferation index, and fusion gene subtypes lacked prognostic significance. Multi-omics analysis of primary versus metastatic tumors revealed striking copy number variations (CNVs) exclusively in metastatic lesions. Specifically, heterozygous losses of SMARCB1 (2/4 metastatic cases) and ATRX (1/4 metastatic cases) were identified; both play critical roles in chromatin remodeling. These genetic alterations were conspicuously absent in primary tumors, suggesting their potential role in metastatic progression. Our findings represent the first demonstration of CNV-driven oncogenic evolution in UTROSCTs, particularly implicating SWI/SNF complex dysregulation in metastatic competence.