Abstract: Objective:To study the clinical pathological characteristics,diagnosis,therapy and prognosis of ovarian immature teratomas(OIT) combined with gliomatosis peritonei(GP).Methods:The histomorphology and immunohistochemistry results of a case with OIT and GP was analyzed under light microscope,and related literatures were reviewed.Results:A huge cystic and solid mass in the abdomined cavity was showed in a 12-year-old girl patient by CT 23.0 cm12.0 cm10.0 cm tumor with intact capsule and adhesion in left accessory was found in the course of operation,which was composed of mature and immature tissues,mostly neurogliatissue derived from epidermal,mesodermal and endodermal elements under microscope.Many grey-white nodules with 0.1 to 0.3 cm in diameter located on the surface of the tumor,pelvic cavity and omentum,which were mature neurogliatissue with clear boundary and no infiltrating.Immunohistochemically,the staining of glial fibrillary acidic protein(GFAP),S-100 protein,vimentin showed positive in the mature glial tissue and cytokeratin staining was positive in the mesothelial cells.The mass tumor and a part of omentum were excised.There was no tumor recurrence and metastasis in the follow-up 26 months.Conclusions:OIT with GP is extremely rare,mature neurogliatissue metastases in omentum indicates that OIT may differentiate up to mature and the prognosis for OIT with GP is good.Surgery and/or chemotherapy are employed according to the stage and pathological differentiation of OIT.