•Dedifferentiated endometrial carcinoma arising from serous carcinoma (null-type P53).•Differential diagnosis including carcinosarcoma, FIGO grade 3 endometrioid carcinoma.•Also need to rule out SMARCA4-deficient uterine sarcoma and other sarcomas.
Keywords: Dedifferentiated endometrial carcinoma; Null-type; P53; Serous carcinoma.
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