Objectives The objective of this study is to report a case of a neuroendocrine tumor arising from a teratoma that was diagnosed with the result of the exeresis of the nodule in the epiploic appendix due to being a case of non-specific and rare presentation.

Methods The methodology used was the study of hospital records and the review of medical literature

Results The mature ovarian cystic teratoma constitutes neoplasm derived from germ cells and presents well differentiated tissues from the three embryonic leaflets. On the other hand, neuroendocrine tumors can develop in several organs. There are few cases in the literature that report the onset of it from a mature teratoma.

The case is of a 57-year-old female patient complaining of progressive growth abdominal mass, who presented abdominal ultrasound and magnetic resonance imaging findings suggestive of adnexal neoplastic lesion. The patient underwent a exploratory laparotomy, and the right pelvic tumor with extraperitoneal extension and epiploic appendage nodule were evidenced and performed. Microscopy and immunohistochemistry confirmed that neuroendocrine tumor was arising from mature teratoma.

Conclusions This work illustrates the importance of the exercise and anatomopathological study of different intraoperative lesions, reporting a case of well differentiated neuroendocrine tumor diagnosed as a result of anatomopathological and immunohistochemical study, since the clinical and appearance of macroscopic lesions are nonspecific.