A, Kaplan-Meier analysis of tumor-free survival of Ctcf+/− (n = 42) and Ctcf+/+ (n = 29) mice, P < 0.0001. B, H&E staining of spontaneous primary histiocytic sarcoma and corresponding lung metastasis from a Ctcf+/− mouse. Scale bars, 100 µm. C, Hematopoietic neoplasms by Ctcf genotype, **** P < 0.0001. D, Kaplan-Meier analysis of tumor-free survival of irradiated Ctcf+/− (n = 52) and Ctcf+/+ (n = 24) mice, P < 0.0001. E, H&E staining of DMBA-induced tumors from Ctcf+/− mice. Left, uterine endometrial adenocarcinoma with epithelial and mesenchymal components. Right, mammary gland adenocarcinoma with areas of spindle cell differentiation (t) and invasion of adjacent skeletal muscle (m); magnification of boxed region (bottom) reveals nuclear atypia (arrowhead). Scale bars, 100 µm. F, Frequency of endometrial lesions (left) and mammary gland histopathology (right) from DMBA-treated mice. Spindle indicates prominent neoplastic spindle cells intermixed within the tumor, ** P < 0.01, * P < 0.05. G, Kaplan-Meier analysis of tumor-free survival in urethane-treated Ctcf+/− (n = 39) and Ctcf+/+ (n = 40) mice, P < 0.0001. H, H&E staining of urethane-induced lung tumors. Scale bars, 1 mm (top) and 50 µm (bottom). I, Distribution of adenomas/adenocarcinomas in each genotype, ** P = 0.002. See also .