CCL2 and carcinoma: While there was no statistical difference in the incidence of carcinomas in the three groups, the increases in granulation tissue count, CD68-positive macrophages, CCL2, the alveolar epithelial cell PCNA index, HO-1, and hyperplasia in the D15 group compared with the D1.5 group was not reflected in the development of lung tumors in these groups.