Often a longitudinal fold of the nuclear membrane accounts for a prominent streak of chromatin. Mitotic figures are common. They exhibit variations in size and shape of their nuclei and may be multinucleated. Chromatin shows coarse clumping. Mitotic figures are abundant.
Cells show loss of intercellular cohesiveness.
Lesions composed of exclusively spindle-A cells are now regarded to behave almost like nevi. Spindle-B tumors may also form a fascicular pattern with palisading of the cells. A final classification is that of a necrotic tumor in which necrosis precludes identification of a cell type. In addition, there may be an associated exudative retinal detachment and also a cystic degeneration of the retina overlying the tumor. Direct invasion of the sclera or optic nerve is much less common.