Granulomatous Inflammatory Response to a Microchip Implanted in a Dog for Eight Years.

An 8 yr old neutered male springer spaniel dog was referred to Texas A&M University, College of Veterinary Medicine for a large, firm, fixed mass, located in the dorsal cervical tissue. The dog was otherwise healthy and had undergone microchip implantation approximately 8 yr prior. Radiographs, ultrasound, and microchip scanner confirmed the presence of a microchip within the mass. The microchip and associated mass were surgically excised, and histopathologic examination revealed granulomatous inflammation surrounding a cracked microchip. This case represents the first report of a granulomatous inflammatory response to a microchip 8 yr after implantation in a dog and highlights an important differential diagnosis.