Detection of kappa- and lambda-expressing cells in the endometrium by in situ hybridization

The detection of kappa- and lambda-expressing cells in endometrial biopsies using in situ hybridization was correlated with the histologic findings. Forty endometrial biopsies were examined in conjunction with kappa and lambda expression in serial sections, recorded as the number of positive cells per 10 ×100 fields. Cells expressing kappa or lambda were found in 39/40 (98%) biopsies with the average total number per 10 ×100 fields as follows: proliferative (n = 13) 13; secretory (n = 6) 16; endometritis (n = 6) 623; polyp (n = 4) 72; adenocarcinoma (n = 6) 677; oral contraceptive effect (n = 5) 8. Many of the B lymphocytes expressing kappa and lambda did not have the cytologic features of plasma cells. The diagnosis of chronic endometritis can be made when the histologic findings of out-of-phase endometrial glands and focal fibrosis are seen with increased plasma cells; in cases where the latter is equivocal, in situ hybridization testing for light chain expression can be useful. Cells expressing kappa and lambda mRNA are relatively common in normally cycling endometrium, implying that mild chronic antigenic stimulation is present in most endometrial tissues. In situ hybridization for light chain expression can be helpful in endometria where only very rare plasma cells are seen; a baseline result would rule out chronic endometritis.