Chronic recurrent multifocal osteomyelitis (CRMO) is characterised by an insidious onset of fever, local swelling and pain in affected bones, and radiological abnormalities suggestive of osteomyelitis. The histopathological features in 14 patients are described. Morphologically CRMO begins as an acute inflammatory process with a predominance of polymorphonuclear leucocytes, which occasionally form an abscess and osteoclastic bone resorption. At a later stage the predominant features are lymphocytes in the inflammatory infiltrates and occasional granulomatous foci and sigans of bone formation. The clinical course may be prolonged for many years.

At re-examination of all osteosarcomata recorded in the Swedish Cancer Registry during the years 1958 to 1968, 11 cases of parosteal osteosarcoma were found. No case of so-called periosteal osteosarcoma was identified. The tumours constituted 1.6 per cent of all proved primary malignant bone tumours. The ages of the 11 patients (six women and five men) ranged from 17 to 62 years (average 33 years). The clinical and histopathological findings of this study and of those collected from a review of the literature suggest the occurrence of two different types of parosteal osteosarcoma: the predominant type is originally benign but has a definite malignant potential, causing metastases after long symptom-free intervals; the other type is highly malignant from the beginning. Primary amputation is recommended for the latter category of tumours, and compartmental, radical en bloc resection followed by regular review is recommended for the former.

Four cases of extra-osseous osteosarcoma were found among 242 cases recorded as osteosarcoma in the Swedish Cancer Registry during the years 1958 to 1968. The tumours occurred in middle-aged and elderly patients. Three of the tumours were situated in the proximal part of the thigh and one in the scapular region. Histopathologically, all tumours were subclassified as osteoblastic osteosarcomas. The patients were treated by primary local excision which in one case was followed by a radical en bloc excision of the entire tumour bed. All cases subjected to simple excision died of metastatic disease five to twenty-four months after diagnosis. The patient treated by en bloc excision is alive and apparently free from disease fourteen years after diagnosis.

The clinical records, radiographs and histopathological material of all forty-one patients recorded as suffering from fibrosarcoma of bone in the Swedish Cancer Registry for the years 1958 to 1968 have been analysed; in addition, four cases were found on histological review of a series of osteosarcomas. From this re-examination, twenty-four patients with genuine fibrosarcoma of bone were identified; twenty-two had primary neoplasms and two secondary. No sex or geographical differences were found. The tumours showed a prevalence for patients in the adult and older age groups. Half of the tumours arose from femoral or tibial metaphysial bone adjacent to a knee joint. All the tumours were of the medullary type. Almost one-third presented with a pathological fracture, and soft-tissue extension had occurred in all but three tumours. In contrast to previous reports, these tumours were more malignant than osteosarcomas and showed a five-year survival rate of only 4-2 per cent. In accessible sites, ablative surgery was used as the primary treatment, Fibrosarcoma of bone is a distinctive lesion and should be distinguished carefully from periosteal and soft-tissue fibrosarcomas because of differences in prognosis and treatment.