FOLR1 and serous adenocarcinoma: Using the PS2 + scoring system, 47% (36/76) of the high-grade serous carcinomas and 43% (3/7) of the low-grade serous carcinomas investigated in this study were classified as FRα-high, which was consistent with previous studies which found frequencies of 44–54% in high-grade serous and 25–40% in low-grade serous EOC [36–39].