The performed Mann–Whitney U test demonstrated that there were significantly higher quantities of both NOTCH1+ and CD117+ stem cells in endometriosis lesions (2.26% (0.08–37.11%) and 0.44% (0.11–15.45%), respectively) compared to adenomyosis lesions (0.13% (0.03–0.79%) and 0.26% (0.02–0.44%), respectively; p < 0.05) (Figure 5). This evidence concerns the gene KIT and endometriosis.