Diffusion lacunae and T2 dark bands in placenta accreta spectrum: MR-pathologic correlation.

A 41-year-old woman with placenta previa and a prior cesarean delivery presented with placenta accreta spectrum (PAS). MRI at 26 weeks of gestation demonstrated an intraplacental hypointense region on diffusion-weighted imaging corresponding to diffusion lacunae (DL). Additionally, irregular hypointense areas on T2-weighted imaging corresponding to T2 dark bands were observed. The entire placenta and uterine wall were sectioned through close collaboration between pathologists and radiologists to match the axial MRI slice plane. MR-pathologic correlation was performed using representative axial MRI and histopathologic findings. Histopathology revealed that DL corresponded to villous-devoid areas suggesting placental lacunae with recent thrombi, whereas T2 dark bands predominantly represented thrombi with lines of Zahn, reflecting the gradual development of thrombi under conditions of blood stasis with residual blood flow. These two MRI findings may therefore represent sequential stages within the same pathological process in PAS.