Primary pulmonary fibrosarcoma associated with Spirocerca lupi infection in a dog with hypertrophic pulmonary osteoarthropathy.

: A dog with severe subperiosteal cortical thickening in all 4 limbs was found at necropsy to have a small noncircumscribed firm lesion in a lung lobe. Microscopically, the lung lesion was a fibrosarcoma that contained several adult nematodes identified as Spirocerca lupi. Lesions were not found in the esophagus or aorta, which are the typical locations for lesions caused by this parasite. Fibrosarcomas have been associated with S lupi infection in the esophagus. In this case, the nematode localized and reached maturity in an aberrant location and apparently participated in the development of a fibrosarcoma at this site.