Retrospective histologic analyses of bone biopsies and of post mortem samples from normal persons of different age groups, and of bone biopsies of age-and sex-matched groups of patients with primary osteoporosis and aplastic anemia show characteristic age dependent as well as pathologic changes including atrophy of osseous trabeculae and of hematopoiesis, and changes in the sinusoidal and arterial capillary compartments. These results indicate the possible role of a microvascular defect in the pathogenesis of osteoporosis and aplastic anemia.

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Summary. In order to evaluate the natural history of essential thrombocythaemia (ET), clinical data and prognostic factors of 143 patients with ET were retrospectively analysed (mean observation time 6·1 Ϯ 4·6 years). In 42 patients the early phase of the disease with initial platelet counts between 250 and 600 × 10 9 /l was assessed. In most early cases, ET was suggested by clinical symptoms (79%) and increased megakaryopoiesis (95%) with abnormal megakaryocytes in bone marrow histology (n ¼ 34) and cytology (n ¼ 5). Other myeloproliferative disorders and reactive thrombocytosis were excluded according to the diagnostic criteria of the Polycythemia Vera Study Group. During follow-up of the 38 early cases not treated cytoreductively at diagnosis, the platelet counts increased to >600 × 10 9 /l in 28 patients (74%) and remained between 450 and 600 × 10 9 /l in 10 patients (26%). In primarily asymptomatic patients (n ¼ 46) with initial platelet counts above (n ¼ 37) and below 600 × 10 9 /l (n ¼ 9) the rates of increase of symptomatic patients were similar at about 7% per year. No influence of the initial platelet count on survival was seen in multivariate analysis of prognostic factors which included all 143 cases. Survival was mainly influenced by the rate of ET-related complications during follow-up (P ¼ 0·002). Analysing the influence of cytoreductive therapy on symptom-free survival, platelet reduction benefited patients under 60 years (19 cytoreductively treated v 65 untreated patients, P ¼ 0·075). The results demonstrate the possible clinical relevance of the early stages of ET and suggest that the features of pathologic megakaryopoiesis in the bone marrow are a more reliable diagnostic criterion than a definite platelet limit. Therefore, further therapeutic studies should include all stages of the disease and all age groups.Keywords: myeloproliferative disorder, early essential thrombocythaemia, prognostic factors, diagnostic criteria, bone marrow histology.Due to the lack of a specific diagnostic marker, the diagnostic criteria of essential thrombocythaemia (ET) established by the Polycythemia Vera Study Group (PVSG) were directed primarily at the exclusion of other myeloproliferative disorders and of reactive thrombocytosis. For diagnosis of ET, a platelet count of 600 × 10 9 /l was considered as an absolute requirement (Murphy et al, 1986). For protocols involving myelosuppressive agents a platelet count of 1000 × 10 9 /l was determined to restrict the erroneous inclusion of cases with reactive thrombocytosis and to avoid possible overtreatment of cases with a mild course of ET (Murphy et al, 1986(Murphy et al, , 1997. In most of the following studies, patients with lower platelet counts were excluded according to the criteria of the PVSG. Such selectivity is acceptable for therapeutic studies. But in the evaluation of the natural course of ET the exclusion of early stages with moderate thrombocytosis below the limit of 600 × 10 9 /l may lead to incomplete recognition of characteristic features of the di...

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Summary. A study has been made of 420 bone marrow biopsies from patients with multiple myeloma (220), idiopathic monoclonal gammapathy (50), reactive plasmacytosis (42) and solitary plasmacytoma (22). Histology and immunohistological parameters were more reliable than cytology in distinguishing a reactive from a neoplastic plasmacytosis. Histological variables were correlated with the clinical features of the patients to determine the factors which were of value in predicting prognosis. Plasma cell maturity and the extent of infiltration in the biopsy by myeloma cells proved to be highly significant in predicting the duration of survival. On the basis of these criteria multiple myeloma was classified into two types: plasmacytic of low‐grade malignancy and plasmablastic of high‐grade malignancy; and into three stages which accurately reflected the progression of the disease. We conclude that a bone biopsy provides useful information for the diagnosis, classification and staging of patients with multiple myeloma.