The diffuse metastatic spread of a solid tumour can mimic a primary osteoporosis, particularly in the absence of localised osteolytic and/or osteosclerotic lesions. Osteoporosis of uncertain aetiology accompanied by bone pain and pathologic fractures should always be thoroughly checked to rule out an underlying malignant condition, especially metastases of neoplasias of the breast, prostate and lungs, among others. The first induces mainly osteoporotic/osteolytic metastases and the second mainly osteosclerotic. Patients with brain tumours are particularly liable to develop osteopaenia/osteoporosis due to a multiplicity of factors. These include drugs, glucocorticoids, antiepileptics, anticoagulants, chemotherapy, radiotherapy, inadequate nutrition, partial immobilisation and possible hemiplegia, and these must all be considered in the medical management. Localised osseous changes, such as vertebral compression fractures, may also occur and must be appropriately handled. Other malignant tumours, such as bronchial cancers, may also cause skeletal lesions, usually paraneoplastic, by means of secretion of parathormone-related proteins (PTHrPs). Various localised changes in the bone are also caused by bone tumours, such as osteosarcomas. It has recently been demonstrated that metastatic breast cancer cells induce an inflammatory stress response in osteoblasts, with production of cytokines that attract osteoclasts, and so establish an environment in which resorption is increased and formation is reduced.