Uterine Tumor Resembling Ovarian Sex Cord Tumors: 23 Cases Indicating Molecular Heterogeneity With Variable Biological Behavior

Uterine tumor resembling ovarian sex cord tumor (UTROSCT) is a rare mesenchymal neoplasm that mainly harbors NCOA1-3 rearrangements with partner genes ESR1 or GREB1. Here, we explored 23 UTROSCTs by targeted RNA sequencing. The association between molecular diversity and clinicopathologic features was investigated. The mean age of our cohort was 43 years (23-65 y). Only 15 patients (65%) were originally diagnosed with UTROSCTs. Mitotic figures ranged from 1 to 7/10 high power fields, of primary tumors and increased from 1 to 9/10 high power fields in recurrent tumors. Five types of gene fusions were identified in these patients, including GREB1::NCOA2 (n=7), GREB1::NCOA1 (n=5), ESR1::NCOA2 (n=3), ESR1::NCOA3 (n=7), and GTF2A1::NCOA2 (n=1). To our knowledge, our group included the largest cohort of tumors with GREB1::NCOA2 fusions. Recurrences were most common in patients with GREB1::NCOA2 fusion (57%), followed by 40% (GREB1::NCOA1), 33% (ESR1::NCOA2), and 14% (ESR1::NCOA3). The recurrent patient who harbored an ESR1::NCOA2 fusion was characterized by extensive rhabdoid features. Both of the recurrent patients who harbored GREB1::NCOA1 and ESR1::NCOA3 had the largest tumor sizes in their own gene alteration groups, and another recurrent GREB1::NCOA1 patient had extrauterine involvement. The GREB1-rearranged patients were of older age, larger tumor size, and higher stage than non-GREB1-rearranged patients (P=0.004, 0.028, and 0.016, respectively). In addition, the GREB1-rearranged tumors presented more commonly as intramural masses rather than non-GREB1-rearranged tumors presenting as polypoid/submucosal masses (P=0.021). Microscopically, nested and whorled patterns were frequently seen in GREB1-rearranged patients (P=0.006). Of note, estrogen receptor expression was weaker than progesterone receptor in all 12 GREB1-rearranged tumors, whereas the similar staining intensity of estrogen receptor and progesterone receptor was observed in all 11 non-GREB1-rearranged tumors (P<0.0001). This study demonstrated that UTROSCTs were present at a younger age in the Chinese population. The genetic heterogeneity of UTROSCTs was correlated with variable recurrence rate. Tumors with GREB1::NCOA2 fusions are more likely to recur compared with those with other genetic alterations.