Fine needle aspiration of osteitis fibrosa cystica

The cytology findings of a fine needle aspiration biopsy from osteitis fibrosa cystica (brown tumor) of the rib in a patient with primary hyperparathyroidism due to parathyroid carcinoma are discussed. Many multinucleated osteoclast-type giant cells, characteristic of either osteitis fibrosa cystica or benign giant cell tumor of bone, were noted. There were also spindly or fibrillary cells with single, ovoid nuclei, probably of stromal origin.