A 1.5-year-old, intact male French bulldog was presented for evaluation of an abnormal mass deformation on the right flank (lateral abdominal). The dog was healthy and had no other abnormalities. The clinical diagnosis of the tumor was uncertain and a surgical resection of the mass was performed after a preliminary evaluation by needle biopsy. Histopathology showed the presence of bone formation in an abnormal location. The diagnosis was primary osseous metaplasia. No signs of neoplasia were observed. Thirteen months after surgery, the canine had a good heath status without further tumor or metastatic symptoms. Osseous metaplasia may be an additional differential diagnosis for abnormal masses in the subcutaneous tissue of the lateral abdominal region of dogs.

Key words: Dog, Histopathology, Osseous metaplasia, Subcutaneous tumor