Figure 3.

Histopathologic subtypes of FOPTS. (a) The spindle cell variant comprises fusiform spindle to polygonal cells. There are often periodic acid Schiff (PAS)-positive thick basement membranes, reminiscent of lens capsule, forming around individual cells. Alcian blue/PAS x 40. (b) The round cell variant is comprised of pleomorphic round cells with a large nucleus-to-cytoplasm ratio. Neoplastic cells are infiltrating the inner retina. Hematoxylin and eosin (H&E) x 40. (c) The osteosarcoma/chondrosarcoma variant comprises mesenchymal cells that demonstrate areas of chondromatous differentiation. Low magnification shows neoplastic osteoid deposition lining the inner pigmented choroid. H&E x 10. Images courtesy of Richard R Dubielzig, DVM, DACVP, and COPLOW