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INTRODUCTION In developing countries, cervical cancer remains the leading gynaecological cancer, though the incidence of endometrial cancer has been increasing, This rise is largely attributed to changes in lifestyle and reproductive patterns among women. Neuroendocrine neoplasms primarily develop in the lungs but can occasionally be found in the gastrointestinal and genitourinary tracts. In this report, we present a case of a 70-year-old woman P5L3D2 diagnosed with large cell neuroendocrine carcinoma (LCNEC) of the endometrium. MATERIALS AND METHODS 70-year-old woman, P5L3D2, presented with 6 months of postmenopausal vaginal spotting. Preoperative workup included a pelvic ultrasound showing a 54 x 37 mm heterogeneous, hyperechoic lesion arising from the endometrium, extending to the endocervical region, and abutting the myometrium with associated thinning. Colour Doppler revealed vascularity within the lesion, and the endometrial-myometrial junction was lost. MRI confirmed a large mass in the uterus (6.6 x 4.6 x 5.4 cm) involving the fundus, body, and upper cervix, hyperintense on T2 and STIR, isointense on T1, with diffusion restriction. The mass infiltrated the serosa of uterus and abutted the small bowel and bladder. She underwent a radical hysterectomy, bilateral salpingo-oophorectomy, and pelvic lymph node dissection. RESULTS Histopathological and IHC evaluation revealed a mixed tumor: 20% well-differentiated endometrioid adenocarcinoma (FIGO grade 2) and 80% large cell neuroendocrine carcinoma (LCNEC, grade 3). Endometrioid component was ER/PR positive; LCNEC showed synaptophysin positivity. Tumor was MLH1/PMS2 negative, ruling out Lynch syndrome. Diagnosis: neuroendocrine carcinoma with endometrioid adenocarcinoma. Pathological stage: pT2b pN0. CONCLUSION Large-cell neuroendocrine carcinoma (LCNEC) of the endometrium is rare and challenging to diagnose, often mistaken for poorly differentiated carcinomas. No specific diagnostic criteria exist, but neuroendocrine biomarkers aid diagnosis. Surgery followed by platinum-based chemotherapy is recommended for early-stage cases, with poor prognosis. Accurate diagnosis is critical, as LCNEC of the endometrium is associated with rapid progression and a poor prognosis.