Intraocular osseous metaplasia presenting as a solid mass in chronic retinal detachment: a case report

BACKGROUND: Intraocular osseous metaplasia is a rare histological finding associated with benign cellular transformation. Its development requires inflammatory cytokines and the process takes many years. Previous case reports of intraocular ossification manifested as linear calcification or white plaques. In contrast, our case presented with a tumor-like solid mass, in which a long-standing chronic inflammatory stimulation may contribute to the stunning appearance. CASE PRESENTATION: This is a 48-year-old woman with past history of advanced Coat’s-like retinopathy and chronic retinal detachment in the left eye for 12 years. She underwent vitreoretinal surgery to prevent phthisis bulbi. During the operation, a 9 mm solid mass was found embedded within the proliferative tissue above the retina and was removed. Pathological findings revealed bone formation in the center of the mass surrounded by fibrous metaplasia and focal gliotic changes. Layers of cohesive cells were found lining on the external side of the mass, and further immuno-histochemical study suggested them retinal pigment epithelial cells. Postoperatively, the retina was attached with stable visual acuity and normal intraocular pressure. CONCLUSION: To our knowledge, the appearance of a tumor-like mass representing intraocular osseous metaplasia in eyes with chronic inflammation or retinal detachment has not been reported in previous case reports. This case emphasizes the importance of considering osseous metaplasia as one of the differential diagnoses of an unknown intraocular mass, especially in eyes with great severity of chronic inflammation. Also, our immuno-histochemical study provided more evidence on the pathological role of retinal pigment epithelial cells in developing ossification.