A 12 year old mixed hound A 12 year old mixed hound was lame for 3 days on the right fore limb - the right shoulder region was painful on palpation - the dog had hypercalcemia - a radiographic study was made of the affected fore limb - Radiographic changes
- Multiple small osteolytic individual bone lesions in the medullary cavity
- The endosteal lesions do not have surrounding reactive new bone
- A single area with focal cortical destruction with periosteal new bone laterally (arrows)
Radiographic diagnosis
- Multiple myeloma is most likely because of the multiple characteristic “punched out” bone lesions
- Metastatic bone tumor is suggested because of the focal destructive cortical lesion with the reactive new bone
- Primary bone tumor is not considered because of the multiple bone lesions without reactive bone
- Hematogenous osteomyelitis is not considered because of the distribution of the bone lesions and the minimal periosteal response
- The radiographic diagnosis of multiple myeloma was confirmed on FNA
Features of multiple myeloma
- Rare tuor accounting for <1% of all malignant neoplasms in dog/cat
- Mean age in cats/dogs is 8-9 years
- Pathologic changes include characteristic “punched out” osteolytic bone lesions seen in 25-66% of cases – Lesions are usually polyostotic – Affected bones are usually axial plus the metaphyses of long bones
- Principle sites are in the vertebrae – Lytic foci are soft, fleshy or gelatinous, dark red nodules replacing trabecular bone
- Renal disease (myeloma kidney) in 33-50% of affected dogs
- High levels of myeloma (M) protein in blood is described as a monoclonal gammopathy - M protein is usually IgG or IgA - Bence Jones proteinuria is found in 35-40% of affected dogs
- Hypercalcemia (15-20% of affected dogs)
From - Tumors in Domestic Animals, DJ Meuten ed 4th ed, 2002 Comments
- The lesions in this patient had a typical “punched out” character
- Atypical character that complicated the radiographic diagnosis was due to – Monostatic lesion - – Single destructive cortical lesion with periosteal response – No vertebral lesions -
