Retinoblastoma extension into the choroid. Pathological study of the neoplastic process and thoughts about its prognostic significance

Free floating retinoblastoma cells in the subretinal space are histologically observed to adhere to the pigment epithelium and to cause local destruction. The pigment epithelium is recognized as an effective barrier against extension of retinoblastoma into the choroid. Evidence of locally successful resistance by the pigment epithelium with subsequent necrosis and calcification of neoplastic cells is presented. Extension of retinoblastoma into the choroid with exposure of thin-walled choroidal blood vessels to neoplastic invasion as well as direct scleral extension is shown histologically and its clinical significance is discussed.