Introduction/Background Gynecological neuroendocrine carcinomas (NECs) are a rare type of cancer that originate from the endocrine cells in the female reproductive system. Gynecological NECs can occur in various locations within the reproductive system, including the ovary, cervix, uterus, and vagina.The diagnosis of gynecological NECs can be challenging due to their rarity and variable clinical presentation

Methodology a 55-year-old Caucasian woman with no significant medical history who presented with abdominal pain and was subsequently diagnosed with a 2x2x1.2 cm intrauterine mass lodged in the endometrium with physical examination and the clinical ultrasound. Further examination was done with an MRI. MRI findings were consistent with our ultrasonographic findings showing a 2.3x2.4x1.4 cm mass inin the endometrium with underwent surgical treatment with hysterectomy with bilateral salpingooophorectomy and omentectomy in 2023 February. First pathological examination was performed by another clinic and the diagnosis was Malignant Mixed Mullerian Tumor (MMMT). However the case was consulted to our pathology department and the diagnosis was changed to NEC. Chemotherapy was planned for the patient received 3 cycles of taxol and cisplatin and continuing treatment with 3 more cycles planned. No recurrence is reported in the last physical examination, MRI and PET scan.

Results Differentiating between gynecological NECs and MMMTs can be challenging, as these tumors may share similar clinical and radiological features. However, accurate diagnosis is critical for selecting the most appropriate treatment approach and predicting patient outcomes. Immunehistochemical markers can be used to help differentiate between these two types of tumors, with gynecological NETs typically expressing markers such as chromogranin A and synaptophysin, while MMMTs may express markers such as p53 and Ki-67 (1)

Conclusion It is important to differentiate between gynecological NECs and MMMTs because these are two distinct types of tumors with different clinical characteristics, prognoses, and treatment options.

Disclosures There are no known conflicts of interest among the authors.