A comparative study of conventional cytology and cell block method in the diagnosis of pleural effusion

Abstract

Background: In a patient with pleural effusion, cytological study (CS) is one of the most useful investigations, especially when malignancy is suspected. Instead of applying only CS, the pleural fluid can be further processed using the cell block (CB) technique, which may augment the diagnostic utility. The aim of this study was to compare the diagnostic yields of CS, CB, and the combination of both, regardless of the etiology of pleural effusion.

Methods: A cross-sectional study was conducted on patients with pleural effusions who underwent thoracentesis from June 2015 to May 2016. All samples were submitted for routine biochemical analysis, CS, and CB histology. The results of cytopathological studies were compared to the final diagnoses.

Results: Out of a total of 353 samples, the final diagnoses included 278 (78.8%) malignancies, 41 (11.6%) infectious diseases, 16 (4.5%) other inflammatory diseases, and 18 (5.1%) transudative pleural effusions. CS and CB provided a similar diagnostic yield (48.7% vs. 49.9%, P=0.69), while the combination of both gave a higher yield (57.2%) (P<0.001, compared with CS). Among 278 malignant pleural effusions (MPE), the diagnostic yields of CS and CB were 61.2% and 61.9%, respectively. Combined CS and CB improved the diagnostic yield to 71.2% (P<0.001). However, both CS and CB had low diagnostic yields in infectious pleuritis, other inflammatory diseases, and transudative pleural effusions.

Conclusions: In MPE, CB provides a similar diagnostic performance to CS, while application of both techniques can significantly increase the diagnostic yield. However, in other pleural diseases, CB and CS had limited values in diagnosis.

Keywords: Cell block (CB); cytology; malignant pleural effusion (MPE); pleural effusion.

Figure 1

Cytologic and histologic findings in a patient with pleural effusion. (A) Cytology specimen demonstrates metastatic adenocarcinoma with tumor cells arranged in three-dimensional configuration (Papanicolaou staining, ×400); (B) corresponding cell block section of the same patient (hematoxylin and eosin staining, ×400).