Implant-associated neoplasia in dogs: 16 cases (1983–2013)

Objective—To characterize clinical and pathological features of implant-associated neoplasms in dogs. Design—Retrospective case-control study. Animals—16 dogs with implant-associated neoplasia and 32 control dogs with osteosarcoma without implants. Procedures—Medical records of dogs with tumors associated with metallic implants (cases) treated between 1983 and 2013 were reviewed. Two dogs with naturally occurring osteosarcoma (controls) were matched to each case on the basis of tumor location, age, and sex. Results—Median time from implant placement to diagnosis of neoplasia was 5.5 years (range, 9 months to 10 years). Pelvic limbs were most frequently affected, including the tibia (8/16) and femur (5/16), with 1 neoplasm involving both the femur and pelvis. Implantassociated tumors most commonly affected the diaphysis (15/16), with osteosarcomas significantly more likely to involve the long bone diaphysis in case dogs than in control dogs with naturally occurring osteosarcomas. Osteosarcoma was the most common tumor, accounting for 13 of 16 implant-associated tumors. For 7 of these osteosarcoma cases, review of histopathology results enabled subclassification into osteoblastic nonproductive (n = 3), chondroblastic (2), osteoblastic productive (1), and fibroblastic (1) groups. Three case dogs had a diagnosis of histiocytic sarcoma, fibrosarcoma, and spindle cell sarcoma. Conclusions and Clinical Relevance—Results of this study highlighted important anatomic differences between spontaneous and implant-associated neoplasia in dogs.