Chronic myeloproliferative disorders (CMPD) are traditionally diagnosed using criteria based on clinical parameters. A framework for an alternative, trephine bone marrow histology-based approach, was provided by the Hanover group of hematopathologist (the "Hanover classification"). The present study describes a single institution experience with the Philadelphia-BCR/ABL negative CMPD diagnosed on the basis of the histopathology of bone marrow in the three consecutive years (2000 - 2002). Among

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... 46 cases of CMPD (M:F=1:1.6), there were 75 cases of idiopathic myelofibrosis (IMF), 45 of polycythemia vera (PV), 93 of essential thrombocythemia (ET), and 33 cases that were unclassifiable on the basis of morphology (CMPD-U). The clinical profiles of the IMF, PV and ET group emerging from the histological examination correlated with the expected clinical features of these diseases. The ET patients were the youngest (median 51 years) compared to PV (59.5 years), IMF (63.9), and CMPD-U (54.7). In 158 cases (74.3%), the biopsy corroborated the preliminary clinical diagnosis of CMPD, and in the half of these cases it refined the clinical diagnosis of suspected unspecified CMPD placing the disease in a particular specific category (ET, IMF or PV). In the remaining cases the biopsy was done due to an abnormality of unknown origin (usually an accidentally discovered thrombocytosis) or the clinical picture suggesting a disease other than CMPD (11.7%). Some cases of CMPD presented with atypical histological features, such as slight megakaryocytic dysplasia in ET (not justifying the diagnosis of IMF), raising the issue of the subjectivity of histological diagnosis. The trephine bone marrow biopsy provides a useful tool for the diagnosis of CMPD, particularly in the early IMF that may present with a clinical picture undistinguishable from ET, but which carries poorer prognosis and requires more vigorous treatment. A special attention should be paid to the CMPD-U group. Its current nosological status (early phases of IMF/ET/PV or distinct entity or entities?) is still unclear and requires further research.