**4.2 Immunophenotypic features of ovarian endometrioid carcinomas**

OECs show diffuse immunopositivity for CK7, PAX8, ER and PgR [83]. Approximately 33% of OECs display membranous and/or cytoplasmic diffuse expression for vimentin [84]. Squamous morules of endometrioid tumours demonstrate

strong CD10 cytoplasmic expression [85] and infrequently CDX2 immunopositive reaction [86]. Endometrioid ovarian carcinomas also exhibit β-catenin membranous and/ or cytoplasmic expression. Nuclear β-catenin expression is correlated with *CTNNB1* genomic alterations and favourable prognosis [77]. Differential diagnosis between high-grade endometrioid carcinomas with solid architectural patterns and high-grade serous carcinomas can be made based on the intense diffuse immunopositivity of WT1, p53 and p16 in HGSCs, whereas ECs display patchy expression for p16, wild-type or mutation-type expression for p53 and loss of WT1 immunoreactivity [87].
