A Prompt Diagnosis of Ascites and Dramatic Effect of Alectinib for Advanced Lung Adenocarcinoma Harboring EML4-ALK Fusion

A 75-year-old never-smoker woman presented with dyspnea and loss of appetite. A mass was identified in the left upper lobe of the lung, and the patient was referred to our hospital. Despite the diagnosis of lung adenocarcinoma via bronchoscopy, anaplastic lymphoma kinase (ALK) immunostaining was negative. Rapid weight gain and abdominal distension caused by ascites prompted fluid testing using the AmoyDx® Pan Lung Cancer PCR Panel. EML4-ALK fusion was confirmed, and alectinib therapy was initiated immediately. The tumor size had decreased significantly, and the patient was discharged on day 34. This case highlights the necessity of multiplex genetic testing even when ALK immunostaining is negative.