Gliomatosis peritonei is associated with frequent relapse but not affects overall survival in patients with ovarian immature teratoma N.-R. Yoon * * Samsung Medical Center, Dept. of Pathology, Seoul, Republic of Korea Objective: Gliomatosis peritonei (GP) associated with ovarian teratoma has known to have no adverse prognostic effect. We investigated the clinicopathological features of ovarian teratoma associated with GP, and compared immature teratomas (ITs) with GP to ITs without GP. Method: We investigated 16 patients with ovarian teratoma with GP and 27 patients with IT without GP, who were diagnosed at Samsung Medical Center (seoul) from January 1995 to August 2010. Results: Six patients with IT with GP (37.5 % of 16 patients) had recurrence. When IT with GP (n=15) was compared to IT without GP (n=27), patient of IT with GP showed larger tumor size (median, 19 cm vs. median 13 cm) (P<0.001), more frequent relapse (40 %, 6/15 vs. 3.7 %, 1/ 27) (P= 0.005), and frequently elevated pre-operative CA125 level (100 %, 12/12 vs. 50 %, 10/20) (P=0.004). Survival curves showed significantly shorter relapse-free survival in patients of IT with GP (P=0.002). Two-year relapse-free survival rates were 59.3 % and 96.3 % in IT with GP and IT without GP, respectively. However, all patients except one case of IT with GP alive. Conclusion: Ovarian IT with GP was characterized by larger tumor size and frequent elevation of preoperative CA125 level, and GP was associated with frequent relapse in patients with ovarian IT.