Context: Immunohistochemical expression of Wilms tumor gene protein (WT1) has previously been described in primary ovarian carcinomas.
Objective: To evaluate differences in WT1 expression among different histologic subtypes of ovarian carcinomas and the correlation to the histologic grade.
Design: Ninety-one primary ovarian carcinomas were reviewed, and 1 representative formalin-fixed and paraffin-embedded tissue block was selected. One slide from each case included in the study was immunostained using the WT1 clone 6F-D2. The immunoreactivity was graded according to the percentage of stained tumor cells. Only nuclear staining was considered a positive reaction. A tumor was regarded as negative if less than 1% of the tumor cells was stained.
Results: All serous carcinomas (28/28) showed WT1 expression, whereas all mucinous (14/14) and all clear cell carcinomas (14/14) were negative. The lone malignant Brenner tumor and 3 (60%) of 5 undifferentiated carcinomas included in the study were also negative. The endometrioid carcinomas showed either no reaction for WT1 or were diffusely positive with more than 50% of the tumor cells stained. All the grade 1 tumors (10/10) were negative, whereas 5 (45%) of the 11 grade 2 tumors and 5 (63%) of the 8 grade 3 tumors showed a positive reaction.
Conclusion: The present study demonstrates differences in immunohistochemical expression of WT1 among different histologic subtypes of primary ovarian carcinomas. Regarding the endometrioid subtype, the expression seems to be correlated to the histologic grade.