Endometrial Giant Cell Carcinoma Integrating Morphology, Immunophenotype, and Molecular Findings in a Misdiagnosed Case

Endometrial giant cell carcinoma (EGCC) is an exceptionally rare and diagnostically challenging variant of high-grade endometrial carcinoma.We describe the case of a 60-year-old postmenopausal woman who was initially misdiagnosed with carcinosarcoma on endometrial curettage.Histopathologic review, immunohistochemical analysis, and comprehensive molecular profiling identified pathogenic tumor protein p53 (TP53), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), and AT-rich interaction domain 1A (ARID1A) mutations, supporting the diagnosis of EGCC and its classification within the p53-abnormal (copy-number-high) molecular subtype of The Cancer Genome Atlas (TCGA).The patient subsequently underwent total abdominal hysterectomy with bilateral salpingo-oophorectomy and bilateral pelvic lymphadenectomy, which revealed no residual carcinoma and no nodal metastasis.Long-term followup was unavailable because the patient missed all surveillance visits, preventing any assessment of prognosis.This report underscores the importance of integrating morphologic, immunophenotypic, and molecular findings to distinguish EGCC from carcinosarcoma and other giant cell-rich uterine tumors, an approach that is essential for accurate diagnosis and for guiding individualized management of these malignancies.