TEMPLATE DESIGN © Endometrial large cell neuroendocrine carcinoma ： a case report Reina Sato, Aiko Kawano, Hiroyuki Shigeta Department of Obstetrics and Gynecology, Yokohama Municipal Citizen’s Hospital, Yokohama, Japan Objectives Endometrial large cell neuroendocrine carcinoma (LCNEC) is extremely rare. We report a case of combined large cell neuroendocrine and endometrioid adenocarcinoma of the endometrium. Papanicolaou smear of the cervix: AGC Endometrial smear: endometrial adenocarcinoma Grade1-2. Endometrial biopsy: endometrial adenocarcinoma Grade1. Serum tumor markers: Preoperative diagnosis: Endometrioid adenocarcinoma, FIGO stage1b (T1bN0M0). Performed operation: Modified radical hysterectomy bilateral salpingo-oophorectomy pelvic lymphadenectomy Postoperative diagnosis: combined large cell neuroendocrine carcinoma and endometrioid adenocarcinoma FIGO stage 1b (T1bN0M0). Conclusions References Endomerial LCNEC is extremely rare. However, when we obtained the result of endometrioid adenocarcinoma by endometrial biopsy, we need to keep in mind that it may contain a small part of another histological cancer including LCNEC. Lorena Posligua, et al., Combined Large Cell Neuroendocrine Crcinoma and Papillary Serous Carcinoma of the Endometrium With Pagetoid Spread. Arch Pathol Lab Med, 2008; 132: Tadashi Terada, Large cell neuroendocrine carcinoma with sarcomatous changes of the endometrium: A case report with immunohistochemical studies and molecular genetic study of KIT and PDGFRA. Pathology, 2010; 206: Kedar K, et al., Large cell neuroendocrine carcinoma of the endometrium: An extremely uncommon diagnosis, but worth the efforts. Journal of Cancer Reserch and Therapeutics, 2011, 7-2: Albores-Saavedra J, et al., Small Cell Carcinomas and Large Cell Neuroendocrine Crcinomas of the Endometrium and Cervix: Polypoid Tumors and Those Arising in Polyp May a Favorble Prognosis. Int J Gynecol Pathol 2008; 27: Case A 61-year-old woman (para4, gravida4) visited our hospital for post-menopausal bleeding. Transvaginal sonography showed endometrial thichening. Results Grossly, a polypoid tumor (3.5×2.5×2.1cm 3 ) was found in the uterine corpus. Magnetic resonance imaging (MRI) showed a mass (3.0×2.5×2.1cm 3 ) in the endometrium and myometrial invasion was suspected in the upper half part of the uterus. Bilateral adnexae were normal. Computed tomography (CT) examination showed no lymphadenopathy. Although we recommended her the postoperative chemotherapy, she denied further treatment. No evidence of recurrence was observed for one year after surgery. Endometrioid adenocarcinoma, G1 Microscopic examination revealed that the tumor infiltrated more than half of the myometrium. Most of the tumor was characterized by endometrioid adenocarcinoma Grade1, however, there was a small portion consisting of solid tumor with necrotic tendency. It was composed of malignant large-sized cells with hyperchromatic nuclei. Immunohistologically, it was positive for synaptophysin and NSE. Large cell neuroendocrine carcinoma Both ovaries and fallopian tubes were unremarkable, and total of 27 lymph nodes dissected by operation were all negative for cancer. CEA 3.0IU/ml CA IU/ml CA IU/ml Immunohistochemical examination: Positive for synaptophysin. Malignant large-sized cells with hyperchromatic nuclei