Cell block samples from malignant pleural effusion might be valid alternative samples for anaplastic lymphoma kinase detection in patients with advanced non-small-cell lung cancer

Aim To evaluate the clinical value of cell block samples from malignant pleural effusion (MPE) as alternative samples to tumour tissue for anaplastic lymphoma kinase (ALK) detection in patients with advanced non‐small‐cell lung cancer (NSCLC). Methods and results Fifty‐two matched samples were eligible for analysis. ALK status was detected by Ventana immunohistochemistry (IHC) (with the D5F3 clone), reverse transcription polymerase chain reaction (RT‐PCR) and fluorescence in‐situ hybridization (FISH) in MPE cell block samples, and by FISH in tumour tissue block samples. In total, ALK FISH results were obtained for 52 tumour tissue samples and 41 MPE cell block samples. Eight cases (15.4%) were ALK‐positive in tumour tissue samples by FISH, and among matched MPE cell block samples, five were ALK‐positive by FISH, seven were ALK‐positive by RT‐PCR, and eight were ALK‐positive by Ventana IHC. The ALK status concordance rates between tumour tissue and MPE cell block samples were 78.9% by FISH, 98.1% by RT‐PCR, and 100% by Ventana IHC. In MPE cell block samples, the sensitivity and specificity of Ventana IHC (100% and 100%) and RT‐PCR (87.5% and 100%) were higher than those of FISH (62.5% and 100%). Conclusions Malignant pleural effusion cell block samples had a diagnostic performance for ALK detection in advanced NSCLC that was comparable to that of tumour tissue samples. MPE cell block samples might be valid alternative samples for ALK detection when tissue is not available. Ventana IHC could be the most suitable method for ALK detection in MPE cell block samples.