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.