Comparison of histopathological findings between idiopathic and secondary epiretinal membranes

To evaluate the histopathological findings of idiopathic and secondary epithelial membranes (ERMs). This study involved 19 ERM cases that underwent pars plana vitrectomy (PPV). ERM specimens were obtained from each patient during PPV and immediately fixed in 10 % formalin. Paraffin sections were stained with hematoxylin eosin (HE) and immunohistochemical analysis was performed with glial fibrillary acidic protein (GFAP), Ki-67, CD34, and nestin antibodies. The 19 ERM cases included 11 idiopathic ERM cases and 8 secondary ERM cases i.e., 2 eyes that underwent PPV for retinal detachment and 6 eyes that underwent PPV for proliferative diabetic retinopathy. HE staining showed that some of the idiopathic ERM specimens consisted of internal limiting membrane. In contrast, numerous invasive cells were observed in the secondary ERM specimens compared to the idiopathic ERM specimens. Immunohistochemical analysis revealed GFAP-positive cells in 4 of the 11 idiopathic ERMs cases, yet no nestin-, Ki-67-, or CD34-positive cells in those cases. In contrast, there were 4 GFAP-positive cases, 2 Ki67-positive cases, 3 CD34-positive cases, and 7 cases including nestin-positive cells. The findings of this study indicate that there are different histological characteristics between idiopathic and secondary ERM and that mature nestin-positive cells in the retina might be related to secondary ERM formation.