Mixed neuroendocrine/Non-neuroendocrine neoplasm (MiNEN) of gastrointestinal lineage arising in an ovarian mature cystic teratoma

•Mixed neuroendocrine/non-neuroendocrine neoplasm (MiNEN) of gastrointestinal lineage arising in an ovarian mature cystic teratoma is extremely rare.•It is important to differentiate the gastrointestinal-type adenocarcinoma arising along with neuroendocrine tumor from a primary mucinous adenocarcinoma of the ovary. SATB2 and CDX2 Immunohistochemical stains play important role in differentiate these two.•This case highlights the careful morphologic evaluation and extensive sampling is crucial to make this rare diagnosis.