OSTEOSARCOMA WITH A PATHOLOGIC FRACTURE IN A SIX-MONTH-OLD DOG

LESLEY PHILLIPS, DVM, DAVE HAGER, DVM, ROBERT PARKER, DVM, DOUGLAS YANIK, DVM

This case history report describes the clinical, radiographic, and histopathologic features of an osteosarcoma with an associated pathologic fracture in a &month-old dog. A Qmonth-old intact male Bloodhound was presented with a primary complaint of a right forelimb lameness of one month's duration. In radiographs, a minimally displaced transverse fracture of the proximal humeral metaphysis was seen. There was extensive cortical bone destruction at the fracture site and minimal periosteal new bone suggestive of a primary bone tumor with a pathologic fracture. Biopsy specimens demonstrated neoplastic mesenchymal cells producing osteoid compatible with a diagnosis of osteosarcoma. This case history report constitutes the youngest reported canine osteosarcoma. Veterinary Radiology, Vol. 27, No. 1, 1986; pp 18- 19.

Key words: osteosarcoma, dog.

STEOSARCOMA COMPRISES 80 percent of malignant bone 0 tumors in dogs. The age of dogs with osteosarcoma ranges from 1 to 15 years, with greater frequency of occurrence at 1.5 and 7.5 years. The incidence is higher in large and giant breed dogs. The most common sites of occurrence include the metaphyseal region of the distal radius, proximal humerus, and proximal and distal tibia and femur.',*

This case history report describes the clinical, radio- graphic, and histopathologic features of an osteosarcoma with an associated pathologic fracture in a 6-month-old dog. Skeletal osteosarcoma has not previously been reported in a dog less than 9 months of ages3

Case History Report

A 6-month-old intact male bloodhound was presented to the University of Florida Veterinary Medical Teaching Hospital with a primary complaint of right forelimb lameness of one month's duration, without history of trauma. Physical examination revealed crepitus in the area of the proximal humerus. Radiographs of the humerus were obtained (Figs. lA, B).

A minimally displaced transverse fracture of the proximal humeral metaphysis was identified. There was extensive cortical bone destruction at the fracture site and minimal periosteal new bone. The extensive cortical bone loss and minimal periosteal new bone was considered an inappropriate

From the Department of Surgical Sciences (Phillips, Parker), Department of Radiology (Hager), and Department of Pathology (Yanik), College of Veterinary Medicine, University of Florida.

Direct all correspondence and reprint requests to Lesley Phillips, DVM, Department of Surgical Sciences, College of Veterinary Medicine, University of Florida, Box J-I 16, JHMHC, Gainesville, Florida 32610.

College of Veterinary Medicine, University of Florida Journal Series No. 53

response for a 1 -month-old untreated fracture. These findings were suggestive of a primary bone tumor with a pathologic fracture. Thoracic radiographs were normal.

The dog was anesthetized and biopsies were taken of the fibrous tissue surrounding the fracture site and fracture ends. These tissue samples were submitted for frozen section and conventional histopathologic examination. Examina- tion of the frozen sections revealed proliferating fibrous tissue and cartilage suggesting callus rather than neoplasia. The fracture was repaired using a single intramedullary Steinman pin and a half Kirschner apparatus, pending further histopathologic results.

Additional biopsy specimens fixed in formalin and stained with H & E were also examined. Neoplastic mesenchymal cells producing osteoid were clearly identified and a diagnosis of osteosarcoma was made. The dog was euthanized at the owner's request and the diagnoses of osteosarcoma and pathologic fracture were again confirmed at necropsy. There was no evidence of metastasis to lymph nodes or lungs at necropsy.

Discussion

This case history illustrates the importance of critical radiographic evaluation of a fracture. A pathologic fracture should be suspected in any acute fracture in which the fracture lines appear indistinct and cortical bone loss is identified. In this case a presumptive diagnosis of osteo- sarcoma was made from the radiographic appearance and the metaphyseal location of the lesion. The diagnosis was confirmed through histopathologic evaluation. This case history report constitutes the youngest reported canine osteosarcoma.

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VOL. 27, No. 1 OSTEOSARCOMA WITH A PATHOLOGIC FRACTURE 19

FIG. I . Lateral (A) and craniocaudal (B) view of the right humerus. Note the minimally displaced transverse fracture ofthe proximal humcral metaphysis. The extensive cortical bone destruction at the fracture site is evident in both views. Note also the minimal amount of periosteal new bone.

REFERENCES

I . Moulton JE. Tumors in domestic animals. Berkeley: University of appendicular skeleton. Compend Contin Educ Small Anim Pract

3. Stookey JL, Terrell TG. Osteogenic sarcoma in a 9-month-old dog. J California Press, 1978:111-25. 19824260-70.

2. Probst CW, Ackerman N. Malignant neoplasia of the canine Am Vet Med Assoc 1972;160:739.