Histogenesis of beryllium-induced bone tumours.

In response to beryllium treatment, irregular bone formation starts mainly in the marrow cavity of long bones, preceding neoplastic growth. Irregular medullary bone formation may be connected with the endosteum, but usually it develops in the bone marrow, independently of the endosteum. Osteogenesis in the bone marrow may be preceded by fibrosis but irregular bone may be formed also without any previous histological changes in the bone marrow. The tumour develops directly from the medullary bone. The prolonged irritation causes abnormal osteogenesis, which ultimately turns into neoplastic proliferation. Thus, the beryllium-induced bone sarcoma is, from histogenesis point of view, a hyperplaseogenic tumour. Irregular bone formation is considered a preblastomatous change, because it is closely connected with the development of the tumour and precedes it in time. The multiplicity of the tumour is explained by the "neoplastic field" theory of WILLIS.