Chronic endometritis: How many plasma cells does it take to make the diagnosis?

3–10% of endometrial biopsies are said to show histologic evidence of chronic endometritis. In this study we correlate the # of plasma cells by H&E to the # of plasma cells by CD138 IHC in endometrial biopsies. Methods 100 endometrial biopsies were selected, excluding specimens with limited material, cancer and menstrual phase. H&Es were reviewed, and the # of plasma cells/10 hpfs were recorded. Additional sections were stained with CD138 antibody (clone B‐A38; Cell Marque, Rocklin, CA). Hot spots of CD138+ cells were recorded as the #/10 hpfs. Histologic findings near the CD138+ cells were also recorded. Results Plasma cells were identified in 29 cases by H&E alone (ave. 2.1, range 1–12) and 90 cases were + for plasma cells by CD138 (ave. 13.9 plasma cells, range 1–190). Of the 29 cases with plasma cells on H&E, CD138 highlighted an average of 24.3, with a minimum of 1. 71 biopsies lacked plasma cells on initial H&E review, but averaged 7.7 plasma cells by CD138. Often, the endometrial stroma contains scattered lymphocytes or mild edema, but lacked the spindled stroma typically associated with chronic endometritis. Conclusions By careful exam on H&E, >1 plasma cells were seen in 29% vs. 90% of endometrial bxs by CD138. These cases include diagnoses of gland‐stromal dyssynchrony, disordered proliferative endometria, and endometrial hyperplasias. The presence of CD138+ plasma cells may not equate to chronic endometritis.