SDC1 and endometrial polyp: In a cross-sectional study by Kuroda et al. of 267 infertile women who underwent a hysteroscopic polypectomy for endometrial polyps, it was proven that the majority of patients had CD138-positive cells in both their endometrium and endometrial polyp samples, which were taken separately, but the number of CD138-positive cells in the polyps was noticeably higher than in the endometrium [37].