CD138-Positive Plasma Cells in the Endometrium of Women with a Caesarean Scar Defect

Objective: This study seeks to assess the prevalence of CD138-positive plasma cells in endometrial biopsies from women undergoing surgery for symptomatic caesarean scar defect (CSD) and examine associations with niche morphology, defect size, symptoms, and surgical approach. Study design: In this prospective single-centre study, women undergoing surgery for symptomatic CSD between January 2024 and June 2026 were included if an endometrial biopsy had been assessed for CD138. Plasma-cell counts were categorised as negative (0 cells/HPF), borderline (1–4 cells/HPF), or elevated (≥5 cells/HPF). Preoperative niche morphology was assessed by transvaginal ultrasound. Associations with CD138 status were tested using Mann–Whitney U and Fisher’s exact tests and multivariable logistic regression. Results: Of 235 surgically treated women, 196 had an assessable CD138 result. CD138 positivity was present in 26 (13.3%); 19 (9.7%) had 1–4 cells and seven (3.6%) > 4 cells. CD138 status was not associated with defect size, uterine position, inclusion cysts, concomitant peritoneal endometriosis, surgical approach, or any recorded symptom. The absence of associations persisted after multivariable adjustment. Conclusions: Endometrial CD138-positive plasma cells were present in a minority of women with symptomatic CSD and did not reflect defect morphology, severity, or symptom burden. Routine CD138 testing cannot be justified on the basis of niche subtype or defect size.