Thrombocytosis and microthrombocytosis: a clinical evaluation of 372 cases.

Data on 372 patients with thrombocytosis (TC), defined as a platelet count over 500 X 10(9)/1, were accumulated in a non-biased fashion. Surgery, per se, was a common cause of TC and malignancy, if uncomplicated by infection, bleeding or surgery, was a less common cause of TC than suggested in previous surveys. The reasons for these apparent differences are discussed. Postoperative TC resolved within 30 days of surgery in the absence of complications. Transient reactive TC due to a variety of causes was accompanied by a significant fall in platelet volume in contrast to the megathrombocytosis found in postsplenectomy and myeloproliferative TC.