9-Year-Old MN Mixed Breed Dog

Signalment & History

A 9 year old MN Mixed breed dog presents for non-painful swelling of the left thoracic limb. This patient had a history of right thoracic limb amputation diagnosed as osteosarcoma. On physical examination, his vitals are normal. On orthopedic examination, no pain or pitting was palpated in the left thoracic limb. The right thoracic limb is absent.

Lateral Craniocaudal


There is moderate pallisading periosteal proliferation along the abaxial margins of the distal humeral diaphysis, and more extensive periosteal proliferation along the axial diaphyseal margins of the radius and ulna. Additionally, the metacarpal bones and proximal phalanxes are affected. Three view thoracic radiographs are obtained.

Right lateral VD Left lateral

There is a soft tissue mass in the ventral periphery of the caudal subsegment of the left cranial lung lobe. Additionally, there is another soft tissue mass in the caudal dorsal region of the thorax at the level of T11-12. There is an irregularly marginated, mineral opaque structure in the right axillary region (the right thoracic limb is absent). There is mild to moderate diffuse osseous proliferation along multiple ribs. Ventral spondylosis deformans are detected throughout the thoracic spine.


This patient is diagnosed with non-aggressive periosteal proliferation of the left distal humeral diaphsysis, radius, ulna, metacarpal bones, proximal phalanges, and ribs. These changes are likely due to the presence of the metastatic pulmonary masses. The bronchial pattern is not likely due to the metastatic pulmonary masses and may be secondary to chronic airway disease. The mineralized right axillary mass may be due to an metastatic lymphadenopathy secondary to the prior osteosarcoma; dystrophic mineralization, or a mineralized granuloma.


Hypertrophic Osteopathy (HO)

  • Generalized osteoproductive disorder of the periosteum
  • Affects long bones of the extremities
  • Usually caused by cardiopulmonary disease or neoplasia
  • When neoplasia is involved, pulmonary neoplasms are most likely
  • Reported in animals with intraabdominal neoplasia without pulmonary involvement
  • Pathogenesis not clearly understood
  • Affected animals have increased blood flow to extremities
    • Overgrowth vascular connective tissue
    • Fibrochondroid metaplasia
    • Subperiosteal new bone formation
  • New bone formation typically begins on digits then extends toward the axial skeleton
  • When joints are involved, large perichondral osteophytes form


Allan GS. Radiographic Signs of Joint Disease in Dogs and Cats. In: Thrall, ed. Textbook of Veterinary Diagnostic Radiology. 5th ed. St. Louis: Elsevier; 2007. p. 317-58.