Concurrent plasma cells and eosinophils in endometrial biopsy specimens: Chronic endometritis or simply inflammatory response?

Chronic endometritis is commonly diagnosed by identification of plasma cells that may be difficult to distinguish from stromal cells or lymphocytes. We correlate the concurrent presence of eosinophils and plasma cells by H&E and CD138 stains in endometrial biopsies. Methods 100 consecutive endometrial biopsies were examined for eosinophils and plasma cells. Cases were stained with anti‐CD138 (mouse monoclonal, clone B‐A38; Cell Marque, Rocklin, CA). H&E and CD138 slides were reviewed, and the number of plasma cells and eosinophils/10 hpfs were recorded. The numbers of plasma cells and eosinophils were recorded again after re‐review of H&Es in areas with high numbers of CD138+ cells. Results 90/100 cases were + for plasma cells by CD138. 57% of the CD138 immunostained subset contained eosinophils by H&E. Utilizing the CD138 stain to map the area of positivity, eosinophils were identified in the area as the plasma cells in 92% of cases and ranged from 1–61/10 hpf. Of the 10 cases lacking plasma cells by CD138, eosinophils were present in 10%. Conclusion Eosinophils are a surrogate marker for the presence of plasma cells in endometrial biopsies. However, plasma cells are more frequently found than eosinophils: 52% contain eosinophils and 90% contain plasma cells. Both may be present as a result of a variety of inflammatory states and are often seen. Clinical correlation is critical for diagnosis of chronic endometritis.