Primary leiomyosarcoma of extragnathic bones. Case report and review of literature.

In a 60-year-old man, a swelling anteromedially just below the knee led to the discovery of an intraosseous leiomyosarcoma. It is the 13th documented case of primary leiomyosarcoma of bone outside the facial skeleton. Clinical and pathologic findings, modes of treatment and therapeutic results are reviewed, and theories of histogenesis discussed. As to the latter, ultrastructural features in our case support the pleuripotent mesenchymal rather than the vascular smooth muscle origin.