It has been followed the microscopical evolution of the malignant melanoma of the choroid. After a stage of local growth, often with necrosis and intratumoral haemorrhages, it invades the neighbouring structures. The invasion of retina is produced at the apex level, making a breach in Bruch's membrane, the tumour becomes likewise a dumb-bell, a mushroom or a clepsydra. When the tumour is in contact with the retina, it produces a proliferation of pigmentary tumoral cells, glial cells and lymphoplasmocytary inflammatory reaction, which emphasize the sensorial retina detachment. The sclera invasion takes place especially in plaqued melanoma, through the points of minimal resistance which are the nervous routes, breaking up the scleral structures. The appearance of rudimentary vessels, with tumoural cells in lumen, constitutes a serous prognostic because of tumoural embolisms.