Prognostic Significance of a New Histologic Grading System for Canine Osteosarcoma

Abstract

Histologic grade is an important determinant in clinical outcome of human osteosarcoma (OS). In this study, the histologic characteristics of primary and metastatic canine OS were evaluated using a new classification system. Histologic characteristics were classified in 166 primary and 34 metastatic canine OS. Prognostic variables for clinical outcome were determined using multivariate analysis. Most OS were histologically characterized by severe to extreme cellular pleomorphism, a variable number of mitoses, small to moderate amounts of matrix, a high percentage of tumor cells, and minimal to moderate amounts of necrosis. Tumor invasion into vessels was present in 117/152 (71%) tumors, and 12/50 (24%) of the regional lymph nodes had evidence of metastasis. Classification of the 166 tumors resulted in seven (4%) grade 1, 34 (21%) grade II, and 125 (75%) grade III OS. In the multivariate analysis, histologic grade III OS and elevated pretreatment plasma alkaline phosphatase (AP) levels were independent predictors of clinical outcome. Dogs with high-grade tumors and elevated AP should be carefully evaluated for the presence of metastatic disease before starting adjunctive therapy protocols.

Prognostic factors of early metastasis and mortality in dogs with appendicular osteosarcoma after receiving surgery: An individual patient data meta-analysis

“…Data from 20 studies were included in this IPDMA, of which 11 studies were previously published (Kurzman et al, 1995;Berg et al, 1997;Kirpensteijn et al, 2002;Vail et al, 2002;Morello et al, 2003;Moore et al, 2007;Bacon et al, 2008;Kow et al, 2008;Phillips et al, 2009;Sottnik et al, 2010). 19 studies reported solely on large breed dogs, while the unpublished study of Dr. Amsellem included 36 small breed canines.…”

Multipotential Osteosarcoma with Various Mesenchymal Differentiations in a Young Dog

“…9,17,20,22 Mesenchymal tissue is known to possess high differentiation potential, and this explains the multipotential characteristics of the neoplasm in this case. In humans, although osseous neoplasms containing malignant chondroblastic or fibroblastic populations have been associated with a better prognosis, 3,12,20,23 there is still much debate in human and veterinary medicine whether histologic features of these neoplasms truly correlate with their prognosis.…”

“…17 Metastatic components may impart a differing histologic appearance in cell type and matrix formation than the primary tumor. 9,17 Secondary or metastatic tumors may affect bone either by direct extension or by hematogenous spread. We present a case of osteosarcoma apparently arising synchronously in multiple long bones in a 1.5-year-old dog.…”

“…In humans, although osseous neoplasms containing malignant chondroblastic or fibroblastic populations have been associated with a better prognosis, 3,12,20,23 there is still much debate in human and veterinary medicine whether histologic features of these neoplasms truly correlate with their prognosis. 3,9,20 The multipotential nature of skeletal osteosarcomas is evident in the abundant fibrosarcomatous or chrondrosarcomatous matrix in many human cases. 3,23,25 Approximately 50% of all human osteosarcomas are predominantly osteoblastic; the remainder may have a primarily chondroblastic, fibroblastic, small cell, or giant cell-rich pattern.…”

Atypical chondroblastic osteosarcoma in the axial skeleton in a dog

“…This finding highlights the importance of necropsy as a post mortem diagnostic method, because it allowed macroscopic evaluation of the tumor, as well as collection of samples for microscopic evaluation. Histopathological analysis is the most indicated test for the diagnosis of osteosarcoma (KIRPENSTEIJN et al, 2002;LOUKOPOULOS;ROBINSON, 2007) and allows classification of the tumor based on formation of osteoid matrix into osteoblastic, fibroblastic, chondroblastic, and telangiectasic subtypes (KIRPENSTEIJN et al, 2002;LOUKOPOULOS;ROBINSON, 2007).…”