title: Increased numbers of pulmonary megakaryocytes in patients with arterial pulmonary tumour embolism and with lung metastases seen at necropsy.
abstract: OBJECTIVE
  To compare the number of pulmonary megakaryocytes in patients with local malignant disease without metastases with the numbers in patients with pulmonary tumour emboli without lung metastases and with those with pulmonary metastases.
  
  
  METHODS
  The prevalence of pulmonary megakaryocytes was studied in 40 necropsies divided into four groups of 10 cases each: normal lungs (I); localised malignancies (II); pulmonary tumour embolism without lung metastases (III); pulmonary tumour embolism and lung metastases (IV). Five fragments (one of each pulmonary lobe) of tissue lung were collected, embedded in paraffin wax, sectioned, and stained by an immunohistochemical method to detect factor VIII related antigen. The number of megakaryocytes was evaluated in 500 high power fields/case.
  
  
  RESULTS
  No differences were observed between groups I and II or between groups III and IV, but there was a 3.5-fold increase in the number of megakaryocytes in the groups with pulmonary tumour embolism or lung metastases compared with those with local neoplasms or normal lungs.
  
  
  CONCLUSIONS
  An increased number of pulmonary megakaryocytes correlated with the presence of tumour cells in the microcirculation of the lungs or parenchymal metastases, but not with local malignancies without lung disease. The permanent siting of tumour emboli may stimulate megakaryocytes to migrate to the lungs, and may increase the release of platelets into the pulmonary circulation.
authors.affiliation: Department of Pathology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Brazil.
authors.forename: F A
authors.initials: FA
authors.lastname: Soares
mesh_terms: D002452:Cell Count; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000556:secondary*; D008533:Megakaryocytes / Q000473:pathology*; D009360:Neoplastic Cells, Circulating / Q000473:pathology*; D011446:Prospective Studies; D011650:Pulmonary Alveoli / Q000473:pathology