BACKGROUND The prevalence of thrombocytosis in lung cancer has been variably reported from 13% to 60%. The vast majority of published data derive from retrospective studies and therefore the estimation of the real prevalence is difficult. PATIENTS AND METHODS We prospectively enumerated platelets in the peripheral blood of 317 consecutive, untreated lung cancer patients. Thrombocytosis was defined as a pletelet count >400.000/mm3. Tumours were histopathologically classified according to the WHO classification and staging was performed according the 2002 version ISS for NSCLC and to the VALSG two stage system for SCLC. RESULTS Thrombocytosis was present in 64 (20.2%) patients and it was unrelated to gender and extent of disease but it was age related: 29/91 (31.8%) in patients ≤50 yrs versus 35/226 (15%) in patients >50yrs old (p=0.001). The distribution of thrombocytosis in the two major histological types was 54/165 (32.7%) for NSCLC and 10/152 (6.6%) for SCLC (
