Multifocal Osteosarcoma

Multifocal osteosarcoma (multicentric osteosarcoma, osteosarcomatosis, multiple sclerotic osteosarcoma), is the occurrence of primary osteosarcoma at two or more sites. Multifocal osteosarcoma can be further classified as synchronous (more than one lesion is seen at presentation) or metachronous (new lesions develop after the initial treatment of primary osteosarcoma).

Multifocal osteosarcoma accounts for less than 5% of cases of osteosarcoma and is thought to be more common in children, who tend to have many symmetric lesions. Older patients tend to have fewer lesions, which are asymmetrically distributed.

There is debate whether multifocal osteosarcoma actually represents multiple primary osteosarcomas or presentation with metastatic disease. In a majority of cases, a large dominant lesion is seen, which may represent the primary lesion.

Some definitions of multifocal osteosarcoma require an absence of pulmonary metastases, which does not appear to be supported by the available evidence. Firstly, no significant difference has been found in clinical and pathologic features of patients with multifocal osteosarcoma with or without pulmonary metastases. Secondly, the absence of pulmonary metastases was initially defined by chest radiography, which is not as sensitive as CT for detection of these metastases.

In children, differential considerations include chronic recurrent multifocal osteomyelitis, hyperparathyroidism with multiple brown tumors, osteopetrosis and osteopoikilosis.

The case above shows a dominant lesion in the left distal femur with a skip metastasis, as well as another lesion at the right greater trochanter.

References

• Daffner RH, Kennedy SL, Fox KR, Crowley JJ, Sauser DD, Cooperstein LA. Synchronous multicentric osteosarcoma: the case for metastases. Skeletal Radiol. 1997 Oct;26(10):569-78.
• Lerner C, Gaca A. Osteosarcomatosis. Pediatr Radiol. 2007 Jul;37(7):724.
• Murphey MD, Robbin MR, McRae GA, Flemming DJ, Temple HT, Kransdorf MJ. The many faces of osteosarcoma. Radiographics. 1997 Sep-Oct;17(5):1205-31.