Objective: To report seven cases of intraosseous leiomyosarcoma and compare them with the cases in the literature.
Design: Retrospective review of histologic, immunohistochemical, and ultrastructural features. Tumors were examined immunohistochemically for proliferative activity and p53 protein accumulation.
Setting: Mount Sinai Hospital, University of Toronto, Ontario, Canada.
Results: The histologic grade of the tumors ranged from I to III. All tumors showed vimentin and muscle-specific actin immunoreactivity and smooth muscle differentiation ultrastructurally. Proliferative activity was demonstrated immunohistochemically in five of the seven cases. Only one tumor showed p53 protein accumulation.
Conclusion: Primary leiomyosarcoma of bone is an aggressive tumor with light microscopic, ultrastructural, and immunohistochemical features similar to leiomyosarcoma of soft tissue. The proliferative activity of these tumors does not appear to correlate with the histologic grade. p53 protein accumulation as detected by immunostaining is not common in these tumors.