The N-methyl-D-aspartate receptor, a precursor to N-methyl-D-aspartate receptor encephalitis, is found in the squamous tissue of ovarian teratomas.

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is the most common antibody-mediated limbic encephalitis and is associated with underlying ovarian teratoma. Previous studies suggest that expression of NMDAR on teratoma neural tissue initiates an autoimmune response to NMDAR in the brain. As some teratomas of patients with anti-NMDAR encephalitis lack neuronal tissue, we questioned if there could be an alternate mechanism of the disease. We performed immunohistochemical analyses for NMDAR and correlated its expression with histology on 10 control teratomas and 5 teratomas associated with anti-NMDAR encephalitis. Both control and case teratomas expressed NMDAR-bearing neural tissue. All 15 teratomas contained large amounts of NMDAR bearing squamous epithelium; in 2 cases this was the only tissue expressing NMDAR. NMDAR-bearing neural tissue is not the sole source of encephalitis in all patients. Furthermore, we speculate that NMDAR expression by squamous epithelium may contribute to the disease development in some patients.