Giant-cell containing "fibrous" lesion of the sacrum. A roentgenographic, pathologic, and ultrastructural study of three cases.

Three similar and unique, predominantly osteolytic lesions are reported in young patients between the ages of 4 and 19 years. Progressive back pain and neurologic deficits were the principal clinical features. The initial roentgenographic impression was that of a malignant tumor either primary or metastic. Despite incomplete resections of a firm, intraosseous and extradural tumor, healing has occurred during the follow-up interval with one interim exception. A spindle-cell stroma containing a variable number of giant cells was the consistent microscopic finding. Ultrastructural studies of one case revealed that the mononuclear spindle cells and giant cells contained cytoplasmic microfilaments similar to those of the myofibroblast. The possible relationship of this tumor to nodular fasciitis and desmoplastic fibroma is hypothesized in the light of the role of the myofibroblast in the fibromatoses and nodular fasciitis.