Myofibrosarcoma of bone

This is a rare malignant counterpart of myofibroblastic tumour

Clinical features

Affects older adults. Myofibrosarcoma also occurs in soft tissues of adults. Related tumours include inflammatory myofibroblastic tumour and inflammatory fibrosarcoma.

Radiology

Produces osteolytic lesions with relative clear margins.

Histopathology

Consist of a mix of cell-rich fascicular and hypocellular areas. The latter may include extremely paucicellular scar-like areas. Variable number of inflammatory cells are present. There may be focal resemblance to leiomyosarcoma. There is variable nuclear pleomorphism. Focal coagulative necrosis is common.

Immunohistochemistry

vimentin	4/4¹
HHF-35	4/4¹
SMA	4/4¹
desmin	1/4¹
calponin	4/4¹
h-caldesmon	0/4¹

Differential diagnosis

conventional osteosarcoma, chondroblastoma and solitary fibrous tumour may all exhibit myoid differentiation.
well-differentiated intraosseous osteosarcoma may have extensive desmoid-like fibrous areas, but shows bone formation and far less atypia than does myofibrosarcoma. It affects adolescents and young adults.
leiomyosarcoma is positive for h-caldesmon.
pleomorphic MFH shows prominent anaplasia with giant cells. Myoid differentiation is, at most, focal.
fibrosarcoma lacks myoid differentiation and lacks an inflammatory component.

References

¹Watanabe, K., Ogura, G., Tajino, T., Hoshi, N., Suzuki, T. Myofibrosarcoma of the bone: a clinicopathologic study. Am J Surg Pathol 2001; 25:1501-7.

This page last revised 19.12.2001.