Graphic depiction of principal components analysis of ovarian and endometrial endometrioid cancers according to histology. Two non-overlapping elliptical regions separate endometrial (upper ellipse) from ovarian (lower ellipse) endometrioid tumor specimens with a 95% confidence interval. The positioning of the ellipses suggests that ovarian and endometrial endometrioid tumors associate according to the organ of origin, rather than histologic subtype. For further details, please see Zorn et al. on page 6422 in this issue.