[Choroidal melanoma and retinal changes]

Literary sources suggest the existence of a new phenotype - retinoinvasive choroidal melanoma (CM). However, the factual evidence of its spreading over the inner retinal surface cannot be dismissed.

To study the capabilities of optical coherence tomography (OCT) in terms of finding the ways CM spreads into the retina based on pathomorphological examination of the eyes enucleated due to CM.

OCT tomograms of 64 eyes with CM (mean tumor elevation - 2.89±0.19 mm, diameter - 9.58±0.43 mm) were studied. Pathomorphological study was conducted on 18 eyes with CM elevated by up to 7 mm and without previous treatment.

OCT revealed signs of melanoma invading into the retina in 49 eyes. Among those signs were: presence of retina/CM aggregation (21 eyes), tearing of Bruch's membrane and retinal pigment epithelium, disturbed differentiation of outer retinal layers (15 eyes). Combination of two types of invasion was found in 11 eyes. Pathomorphological study showed low mitotic activity of CM and the presence of a small number of fine-local necroses and hemorrhages. Invasion of CM into the retina was determined in 13 eyes. Retinal invasion began with local destruction of Bruch's membrane (BM) and was often limited by the photoreceptor level, disturbing architectonics of the retina and nuclear layers. Large CMs were accompanied by rough destruction of the Bruch's membrane, tumor cells - in the edematous retina with cystoid dystrophy, in its inner layers, invading into the vitreous body. Infiltration of the retina to inner nuclear layer was accompanied by its transudative detachment and cystoid dystrophy.

Invasion of CM into the retina affecting all of its layers imposes use of OCT to examine the integrity of the retina, even with a tumor of small thickness. Tumoral infiltration of the retina and localization of tumor near the optic disc are two contraindications for local endovitreal resection. Brachytherapy requires consideration of tumor characteristics and thickness of the retina for calculation of apical radiation dose.