Mesothelial Cells and Tuberculous Pleuritis

We read with great interest the report by Kam-Yung Lau (Chest 1989; 96,2:438-39) of two cases of pleural tuberculosis with significant numbers of mesothelial cells. We wish to make several comments. As the author points out, at present it is believed that this finding almost excludes a diagnosis of tuberculous pleural effusion. However, various data in the literature and our own experience do not support this concept. Actually, we have recently found numerous mesothelial cells in a patient with tuberculous pleural effusion. Moreover, there are several series—some extensive—in which the presence of significant numbers of mesothelial cells was not a rarity. For instance, in a retrospective study of 88 tuberculous pleural effusions, the authors found more than 5 percent mesothelial cells in 13 patients (15 percent).1Jimenez LA Rodriguez PF Cantos CA et al.Pleuritis tuberculosa: crítica de las técnicas de estudio de la biopsia pleural.Arch Broncopneumol. 1986; 22: 160-165Crossref Scopus (2) Google Scholar Other studies have shown similar results.2Muñoz LF Rodriguez PF Martínez PF Cantos CA López MJ. Pleuritis tuberculosa. Sistemática diagnóstica.Arch Broncopneumol. 1983; 19: 51-56Crossref Google Scholar, 3Hirsch A Ruffie P Nebut M Bignon J Chretien J. Pleural effusion: laboratory test in 300 cases.Thorax. 1979; 34: 106-112Crossref PubMed Scopus (144) Google Scholar In pleural tuberculosis (as in other chronic pleural effusions), the extensive inflammation of both pleural layers prevents the exfoliation of mesothelial cells into the pleural space. However, in an early phase when the inflammatory process is acute and not extensive, it is possible to find numerous mesothelial cells. In fact, in patients with tuberculous pleuritis the disappearance of mesothelial cells on serial thoracocentesis has been observed as the white cell count changes from neutrophil to lymphocyte predominance.1Jimenez LA Rodriguez PF Cantos CA et al.Pleuritis tuberculosa: crítica de las técnicas de estudio de la biopsia pleural.Arch Broncopneumol. 1986; 22: 160-165Crossref Scopus (2) Google Scholar Therefore we think, in accordance with Kam-Yung Lau, that pleural tuberculosis remains a diagnostic possibility in the presence of more than 5 percent mesothelial cells. If the thoracocentesis is performed in an early phase of the disease, this finding is not exceptional.