According to the proposed algorithm [17] for the interpretation of immunohistochemical markers of ovarian cancer, WT1 positivity suggests serous carcinoma, although approximately 10% of HGSCs can be WT1-negative and aberrant TP53 and/or diffuse p16 (CDKN2A) expression are typical for HGSC, whereas a TP53 wild-type pattern and patchy p16 expression and WT1 positivity suggest a low-grade serous carcinoma. The gene discussed is CDKN2A; the disease is ovarian cancer.