Endometriosis-derived EEOs exhibited elevated baseline γH2AX (phosphorylated histone H2AX) immunofluorescence compared with controls (2.32 ± 0.44 vs. 1.00 ± 0.28, <i>p</i> = 0.05), indicating increased DNA double-strand break accumulation. Here, H2AX is linked to endometriosis.