CD163 and periapical granuloma: However, these studies either compared the M1 proportions in radicular cysts and in apical granuloma,4 which lack direct comparison between the M1 and M2 subpopulations in the same pathological state; or appraised the M1/M2 ratio via only a general marker of macrophages (CD68) and an M2-specific marker (CD163),23 which may cause bias when quantifying the M1 percentage.