Genuine giant-cell tumour of bone; a combined cytological, histopathological and ultrastructural study.

Three patients with a giant-cell tumour of bone were studied clinically, roentgenologically and morphologically, using cytological, histopathological and electron microscopic methods. The tumours were composed of giant cells possessing a great number of mitochondria and stromal cells exhibiting prominent endoplasmic reticulum and Golgi complex. Mitotic activity was only found among the stromal cells. Autophagic vacuoles, lysosomal bodies and degenerative changes of varying severity were found mainly or exclusively among the giant cells, which may indicate that these cells represent an involutionary form of tumour cell. The giant-cell tumours of bone are believed to arise from undifferentiated cells of the bone marrow. Fine-needle aspiration biopsy represents a valuable complement to histopathological examination in the identification of giant cell lesions and diagnosis of genuine cell tumours of bone.