Solid variant of aneurysmal bone cyst.

BACKGROUND AND METHODS: Of the 200 cases of ABC in the Rizzoli Institute files, 15 had solid features on both gross and histologic examination. Inasmuch as fibrous proliferation with giant cell and bone production along with fibromyxoid areas and small aneurysmal spaces were found in the solid parts of the aneurysmal bone cyst, a grossly solid and radiographically osteolytic bone lesion with these microscopic features was called a solid aneurysmal bone cyst. Some authors call the same lesion extragnathic giant cell reparative granuloma.

RESULTS: Sixty percent of the patients were female. The metaphysis was the preferred location in the long bones (8/11). Radiographic appearance was not specific, and sometimes a malignant lesion was very difficult to rule out. In seven patients, the lesion was considered radiographically "aggressive." Intralesional excision (curettage) in 12 patients and marginal resection in 3 patients with diaphyseal location was effective in controlling the lesion. No recurrence was detected after a mean follow-up of 59 months.

CONCLUSIONS: High proliferative activity of the benign-appearing proliferative spindle cells, often with fairly abundant mitoses, associated with benign giant cells and immature bone production are the features of this pseudosarcomatous hyperplastic lesion. It is sometimes is mistaken for a malignant tumor.