Chondrosarcoma is an uncommon malignant neoplasm in which the neoplastic cells produce chondroid and varying amounts of matrix. This tumor is the second most common primary skeletal tumor in animals. In our case, radio-logical and histopathological findings supported the final diagnosis of chondrosarcoma in a six-year-old male cat weighing 6.3 kg with a large and solitary mass in the right humerus. The shoulder joint had a limited range of motion. Radiographs were obtained from the raised growth. The mass was surgically excised for histopathological evaluation. Microscopically, the mass was composed of bundles and nests of neoplastic mesenchymal cells. Histo-pathologically, multiple-sized lacunae within a homogenous cartilage matrix were observed. There was marked anisocytosis and anisokaryosis. Neoplastic chondrocytes and oval cells with 1 to 3 nucleoli were seen. Based on the macroscopic, radiological, and cartilaginous differentiation of tumor cells and matrix, the mass was diagnosed as well-differentiated chondrosarcoma

BACKGROUND: Fracture healing is one of the important issues in medicine and veterinary. Therefore, finding new tech-niques with fewer side effects and faster healing is taken into consideration. OBJECTIVES: This study was conducted to evaluate the effect of the composites of micro ostrich eggshell (μ-OES) and hydroxyapatite (HA) composite on the healing of bone defect in rat calvarium. METHODS: Defects of 7 mm were made by a trephine in the calvaria of 45 male Wistar rats. The animals were divided into three groups and the defects in each group were filled with micro-composites that contained ostrich eggshell or HA or were left empty. The animals were euthanized at three different time points of 14, 28, and 42 days post-operation. Histological and serological assessments, such as measuring alkaline phosphatase were carried out at the same time points. RESULTS: Significant differences were observed in the granulation tissue formation of the treatment and control groups 14 days post-operation (p ≤0.05). The difference between μ-OES and HA treatment groups was not statistically significant (p >0.05). On days 28 and 42, there were no significant differences between the groups. However, in the center of the defect, the mean of healing in the μOES group was higher than the two other groups. CONCLUSIONS: In conclusion, the results of this study indicated the potential efficacy of μOES as a bone substitute in a rat calvarial defect model