Necrotic mature ovarian teratoma associated with anti-N-methyl-D-aspartate receptor encephalitis.

A 20-year-old female with a diagnosis of autoimmune encephalitis against N-methyl-D-aspartate receptor was found to have a 13 mm teratoma in the left ovary. The tumor had undergone massive coagulative necrosis within a normal ovary, a previously unreported feature. Necrosis of a mature cystic teratoma is very rare in the absence of ovarian torsion. It is proposed that necrosis may have induced a massive liberation of neuronal antigens. The vast majority of the tumors associated with this newly described condition are ovarian teratomas containing neural tissues. In this paper, we review their different histopathological aspects that may explain the relative incidence of various tumor types associated to this form of encephalitis. Anti N-methyl-D-aspartate receptor encephalitis has now become the most frequent autoimmune disorder associated with ovarian teratoma.