FOXG1 and undifferentiated ovarian carcinoma: Positive staining of FOXG1 was observed in 100.0% (9 out of 9) serous, 66.7% (4 out of 6) mucinous, 84.6% (11 out of 13) endometrioid and 33.3% (1 out of 3) clear cell/undifferentiated ovarian cancer (Table 2) (Figure 2B–E).