So-called massive retinal gliosis: A critical review and reappraisal

Massive retinal gliosis, a nonneoplastic retinal glial proliferation, was first described in detail over 25 years ago, before the era of immunohistochemistry, in a series of 38 cases-to which can be added 30 case reports or small series (no more than 3 cases) subsequently. We analyze a new series of 3 nontumoral intraretinal glioses and 15 cases of tumoral retinal gliosis, not all of which, strictly speaking, were massive. The data from this series are compared with the findings in previously published cases. Included are 2 cases of massive retinal gliosis diagnosed from evisceration specimens. In reviewing all published and current cases, we were able to establish 3 subgroups of retinal tumoral glioses rather than a single "massive" category: focal nodular gliosis, submassive gliosis, and massive gliosis. Among 43 reported cases, including the present series, but excluding the previous large series of 38 cases in which substantial clinical data were omitted, there were 19 men and 24 women. Their mean and median ages were 36.2 years and 36 years, respectively, with a range of 2 to 79 years. All lesions were composed of mitotically quiet, compact spindled fibrous astrocytes devoid of an Alcian blue-positive myxoid matrix. The most common associated ocular conditions were phthisis bulbi and congenital diseases or malformations. Histopathologically, all 3 tumoral categories were accompanied by progressively more extensive fibrous and osseous metaplasia of the pigment epithelium, the latter forming a clinically and diagnostically useful, almost continuous, outer rim of eggshell calcification in the submassive and massive categories that should be detectable with appropriate imaging studies. In decreasing order of frequency, microcysts and macrocysts, vascular sclerosis, exudates, calcospherites, and Rosenthal fibers were observed among the proliferating fibrous astrocytes. Immunohistochemistry was positive for glial fibrillary acidic protein in all cases and nestin in most (an intermediate cytoplasmic filament typically restricted to embryonic and reparative neural tissue). The nonneoplastic nature of all categories of gliosis was confirmed by absent TP53 (tumor suppressor gene) dysregulation, Ki-67 negativity, and intact p16 expression (the protein product of the p16 tumor suppressor gene) in the overwhelming majority of cases. These findings indicate an intrinsic attempt to regulate and maintain a low level of glial cell proliferation that becomes unsuccessful as the disease evolves. The categories of tumoral proliferation appeared to constitute a spectrum. We conclude that focal nodular tumors encompass lesions previously called retinal vasoproliferative lesions, which display the same histopathologic and immunohistochemical findings as 3 major categories of retinal gliosis characterized herein.