An extremely rare aggressive primary uterine neoplasm, originating from neuroendocrine cells scattered within the endometrium. Macroscopic characteristics are a bulky frequently polypoid mass with abundant necrosis located in the uterus. Histological characteristics are rosette-like and cord-like structures consisting of small rounded cells with oval nuclei and scarce cytoplasm. Patients often present with dysfunctional uterine bleeding, pelvic or abdominal mass and abdominal pain, especially in later stages of the disease. Symptomatic metastatic spread or symptoms related to a paraneoplastic syndrome such as retinopathy or Cushing syndrome due to ectopic ACTH production may be associated. [from SNOMEDCT_US]