Incidence of anti-NMDAR encephalitis in patients undergoing resection of ovarian teratoma in a single institution

Objective: The objective of this study was to determine the incidence of anti-NMDAR encephalitis in patients in whom a teratoma was removed. As far as we know, there has been no report on the incidence of anti-NMDAR encephalitis in patients in whom a teratoma was removed. Methods: This study was a single-institutional observational study. We enrolled patients who were diagnosed with teratoma in the Department of Pathology, Sapporo City General Hospital during a nine-year period between January 2008 and December 2016. Results: In Sapporo City General Hospital, 6 NMDAR encephalitis cases were detected during the 9-year period. In the same 9-year period, a pathological diagnosis of teratoma was made in 343 cases in the hospital. Anti-NMDAR encephalitis patients with a teratoma accounted for only 1.17% of all teratoma patients. Three of the 4 anti-NMDAR encephalitis patients with a teratoma underwent second removal of a teratoma, and no nervous tissue was detected pathologically. Conclusions: In this study, we determined the association between teratoma with anti-NMDAR encephalitis and teratoma without anti-NMDAR encephalitis in cases in a single institution. As far as we know, this report is the first report on the incidence of anti-NMDAR encephalitis in teratoma patients.