Abstract

To the Editor:

In patients with diagnostic pleurisy, it is important to examine which type of leukocytes in pleural effusion is predominantly increasing. For example, if neutrophils are predominantly present, bacterial infection is suggested. If lymphocytes are predominant, tuberculosis or malignancy is considered to be the cause. If an increase in eosinophils is observed, it is said that the probability of malignancy being the cause is high. ^1–3 However, there are no reports in the literature regarding an increase in basophils. Therefore, in a study comprising 42 cases, we have examined the cause of basophilic pleural effusion, which is defined as pleural effusion in which basophils account for 5% or more of leukocytes. The results are as follows. The incidence of basophilic pleural effusion was 3.6% in our hospital from 1996 to 2002 (42 of 1,178 cases of pleural effusion retention). Seven cases were transudates, and 35 were exudates. The causes of exudates included pneumothorax in 10 cases (28%), pneumonia in 9 cases (25%), malignancy in 7 cases (20%), postoperative effusion in 2 cases (6%), idiopathic in 2 cases (6%), drug allergy in 2 cases (6%), and pulmonary infarction, parasites, and contusion in 1 case (3%). There were no cases of tuberculosis. On the basis of these results, we suggest that tuberculosis is not the cause of basophilic pleural effusion and that the probability of malignancy is low, whereas there is a high likelihood that benign diseases such as pneumothorax or pneumonia cause this problem.