Feline Chondroblastic Osteosarcoma: Comparative Analysis by Pathology Techniques

Abstract

Even though primary bone tumors are considered uncommon in cats, osteosarcoma is the most common, with a prevalence of 70% to 80% of all primary bone tumors reported in this species. However, the number of cases reported are still scarce when compared to those reported in dogs. The goal of this study was to diagnose, through necropsy and histopathology, a case of feline chondroblastic osteosarcoma presented to a private practice in Brazil, describing the macroscopic and microscopic findings. The necropsy was performed at the Pathology Laboratory of Paulista University, located in São José dos Campos, Brazil, using an adaptation of the Ghon method, developed by Professor Janaína Duarte, DVM, PhD. Histopathology was performed by a veterinary diagnostic laboratory located in São Paulo, Brazil.A female, spayed, 12 years old, domestic short hair cat, was presented to an ophthalmology specialist practice with a complaint of suspected glaucoma, which a skull radiograph later showed to be, in fact, exophthalmus caused by a mass in the left eyeball topography, with loss of definition of the zygomatic bone’s rostral aspect and the adjacent maxilla. Euthanasia was performed due to worsening of the general state and economic limitations to follow further diagnose and treatment. Necropsy revealed a lobulated, semi‐hard, pale red mass, measuring approximately 4.0 × 3.0 × 1.0 cm, adhered to the left mandible vertical ramus and pressing against the left eyeball. Transverse cutting showed a translucent, whitish, partially mineralized surface. Histopathology exhibited proliferation of spindle shaped cells, with marked degeneration, cytoplasmic retraction and acidophilic staining, arranged in disorganized bundles, permeated by immature and mineralized osteoid matrix. The nuclei were rounded, hyper‐chromatic with occasional nucleoli evidence. Figures of mitoses were not identifiable due to cellular degeneration. It was also seen that between the cells there were multiple focuses of marked chondroid tissue proliferation, highly suggestive of chondroblastic osteosarcoma.Macroscopic findings during necropsy showed a mass with malignant and invasive biological behavior, affecting adjacent structures such as the eyeball and the zygomatic arch, which is consistent with those of histopathology that showed proliferation and marked degeneration of atypical spindle shaped cells with infiltration of the chondroid matrix by osteoid tissue.Location of the mass, filling the left eye orbit (arrow).Figure 1Proliferation of spindle snapped cells permeated by osteoid and chondroid matrix.Figure 2