Material and Method: Forty patients with lung cancer and exudative pleural effusions were included. Ten mililiters of fresh pleural fl uid was obtained by thoracentesis from all patients in the initial evaluation. The pleural fluid sample was divided into two equal parts. One part was subjected to conventional smear and the other to the cell block method. Conventional smears were stained with May-Grünwald-Giemsa and Hematoxylin-Eosin. Cell block sections were stained with Hematoxylin-Eosin and mucicarmine. Conventional smear findings were grouped as “benign cytology” or “malignant cytology”. Th e cell block sections were evaluated for the presence of single tumor cells, acinary or papillary pattern, solid islands and staining with mucicarmine.

Results: There were 20 patients each in the benign and malignant conventional smear group. In the benign group, adding the cell block method to conventional smear provided a diagnosis of malignancy in 4 more patients and the diagnosis of malignant effusion was increased by a ratio of 10% (4/40). In the malignant group, adding the cell block technique provided the subtyping of lung cancer as adenocarcinoma in 7 patients (7/20, 35%).