Objective: Folate receptor alpha (FRα), which is expressed in various cancers, is a potential therapeutic target. However, its expression and clinical significance in uterine (UCS) and ovarian carcinosarcoma (OCS) remain to be elucidated.
Methods: This retrospective study included patients with gynecologic carcinosarcoma who underwent primary surgery between 1997 and 2019 at our institution. Immunohistochemical staining of surgical FFPE specimens was performed for FRα and HER2. FRα was evaluated using the H-score and the 4-tired scoring system (0 to 3+). Subsequently, FRα expression (≥5% of tumor cells with ≥1+ intensity) and FRα-high (score 2+ and 3+) were evaluated. HER2 was scored according to the modified ASCO/CAP criteria. The association between FRα-high and clinicopathological features, HER2 expression, and survival was assessed in UCS.
Results: A total of 120 patients with UCS and nine patients with OCS were included. In UCS, FRα expression was observed in all patients, whereas FRα-high status was present in 20% of patients. Among HER2-negative UCS, 34% exhibited FRα-high. No significant association was observed between clinicopathological characteristics and FRα status. During the follow-up period (median 34.5 mo), FRα-high was not strongly associated with progression, free survival, and overall survival. All the OCS tumor specimens showed FRα-high expression.
Conclusions: FRα expression was observed in all the UCS and OCS specimens, including HER2-negative UCS patients. This widespread FRα expression suggests that FRα-targeted therapies may hold promise for the treatment for gynecologic carcinosarcoma. However, in uterine carcinosarcoma, no significant relationship was observed between FRα expression and clinicopathological features or prognosis.
Keywords: Folate receptor alpha; HER2; Immunohistochemistry; Ovarian carcinosarcoma; Prognosis; Uterine carcinosarcoma.
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