Objective: To explore ALK protein expression and gene fusion in formalin-fixed and paraffin-embedded (FFPE) specimens obtained from lung cancer by bronchoscopy, and to investigate the relationship between ALK status and clinicopathological characteristics of the patients.
Methods: Seventy-four FFPE samples obtained from lung adenocarcinoma by bronchoscopy were tested for ALK protein expression and gene fusion respectively by immunohistochemistry (IHC) using Ventana D5F3 antibody and fluorescence in situ hybridization (FISH) using ALK break apart probe.
Results: sixty-five of the 74 samples were successfully tested by FISH (87.8%, 65/74) . There were 5 FISH-positive cases (7.7%, 5/65) , all with advanced stage carcinoma. Among these five FISH-positive cases, 3 were IHC-positive (4.1%, 3/74) and 2 IHC-negative cases. All the other 69 samples were IHC-negative, including nine FISH-uninformative samples (7 samples were less than 50 tumor cells and 2 samples with weak FISH signal). Both ALK IHC and FISH results were not correlated with age, sex, history of smoking, histological classification, differentiation and lymph node metastasis.
Conclusions: Bronchoscopic specimens of lung cancer can be used to detect ALK expression and gene fusion. Immunohistochemistry in combination with FISH test may be more favorable for ALK test.