Immunohistochemical Expression and Significance of Preferentially Expressed Antigen in Melanoma (PRAME) in Gynecological Tumors: A Single-institution Retrospective Analysis.

Background/aim: Although preferentially expressed antigen in melanoma (PRAME) has been used as a diagnostic marker for malignant melanoma (MM), it is also expressed in various other malignancies. PRAME expression is rarely reported in female genital tumors. This study aimed to evaluate PRAME expression and its significance in gynecological malignancies.

Patients And Methods: We conducted PRAME immunostaining in 135 specimens, including 85 endometrial carcinomas (ECs), five uterine sarcomas (USs), 28 cervical carcinomas (CCs), and 17 ovarian carcinomas (OCs). PRAME immunoreactivity was evaluated using a semi-quantitative histoscore method.

Results: PRAME was expressed in 82 (96.5%) ECs, 15 (88.2%) OCs, three (60.0%) USs, and eight (28.6%) CCs, with mean histoscores of 174.6, 108.9, 32.2, and 27.5, respectively. EC exhibited elevated PRAME expression levels compared to other tumors, with immunoreactivity being higher in endometrial endometrioid carcinoma (EEC) than that in other EC types. Grade 1 EEC exhibited higher PRAME expression levels than grade 2-3 EECs.

Conclusion: PRAME over-expression in gynecological tumors supports the notion that this marker should not be regarded as specific to MM alone. EC exhibited higher PRAME expression than CC and OC, and low-grade EEC displayed higher PRAME immunoreactivity than other EC types. Our findings suggest that PRAME immunostaining can be useful to distinguish EEC from ovarian endometrioid carcinoma and endocervical adenocarcinoma. PRAME over-expression can also help differentiate non-aggressive EC from aggressive EC.