PD-L1 expression, morphology, and molecular characteristic of a subset of aggressive uterine tumor resembling ovarian sex cord tumor and a literature review

Background Uterine tumors resembling ovarian sex cord tumor (UTROSCT) is a rare neoplasm of unknown etiology and has undetermined malignant potential. The emergence of recurrent UTROSCT case reports has led to its initial identification as a tumor of low malignancy potential. Owing to its low incidence, we currently lack any in-depth studies regarding the subset of UTROSCTs that may be aggressive in nature. Here, we sought to identify unique characteristics in aggressive UTROSCT. Methods 19 cases of UTROSCT were collected. Their histologic and tumor immune microenvironment were evaluated by three gynecologic pathologists. The gene alteration was also detected by RNA sequencing. For later analyses regarding differences between benign and malignant tumors, we supplemented our 19 included cases with additional reports from the literature. Results Interestingly, we found PD-L1 expression in stromal tumor-infiltrating immune cells (stromal PD-L1) was markedly higher in aggressive UTROSCT. Patients with high stromal PD-L1 (≥ 22.5 cells/mm 2 ) had worse prognosis. When our cases were added with previous cases identified in the literature, we discovered that aggressive UTROSCT was more likely to have significant mitotic activity and NCOA2 gene alterations than benign UTROSCT. Consistence with those results, patients with significant mitotic activity and gene alteration of NCOA2 had worse prognoses. Conclusions Collectively, high expression of stromal PD-L1, significant mitotic activity, and gene alteration of NCOA2 may be useful markers to predict aggressive UTROSCT.