Application of pleural effusion cell blocks for immunohistochemistry and EGFR gene mutation testing for advanced lung cancer.

In the present study, the diagnostic capability of pleural effusion cell blocks for immunohistochemistry and epidermal growth factor receptor (EGFR) mutation detection in advanced lung cancer was explored. Samples of pleural effusion were collected from 231 patients with advanced lung cancer, treated at Weifang No. 2 People's Hospital (Weifang, China) from July 2018 to December 2022, and were transformed into cellular blocks by embedding them in paraffin. Lung cancer subtypes were determined using immunohistochemical staining, and EGFR gene mutations were identified through the use of the amplification refractory mutation system technology (ADx-ARMS). Of the 231 specimens analyzed by immunohistochemistry, 222 were adenocarcinoma, seven were small cell carcinoma and two were squamous cell carcinoma. EGFR testing was performed on 161 lung adenocarcinoma cases, revealing an EGFR mutation rate of 52.8% (85/161). The mutations discovered in the EGFR gene encompassed L858R in exon 21 (49 instances), deletion of exon 19 (31 instances), L861Q in exon 21 (2 instances), G719X in exon 18 (1 instance), a co-mutation of G719X/L861Q (1 instance) and a co-mutation of S768I/G719X (1 instance). The EGFR mutation rate was significantly higher in female patients with lung adenocarcinoma (32.30%) compared with that in male patients (20.50%) (P<0.05). Furthermore, patients with EGFR-mutant lung adenocarcinoma undergoing treatment with EGFR tyrosine kinase inhibitors exhibited a significantly extended survival rate compared with those with wild-type EGFR receiving chemotherapy. In conclusion, the present study demonstrated that immunohistochemistry with pleural effusion cell blocks can aid in clarifying the histological subtype of lung cancer, and enable EGFR mutation detection, which can effectively guide molecular targeted therapy.