Alectinib is a highly selective tyrosine kinase inhibitor of anaplastic lymphoma kinase (ALK) that is approved as first-line treatment in adult patients with ALK-positive non-small cell lung cancer (NSCLC) and as second-line in patients previously treated with crizotinib, and has been shown in the literature to significantly prolong progression-free survival compared to chemotherapy in patients with advanced non-small cell lung cancer. The authors describe a clinical case of a 24-year-old woman with malignant massive pleural effusion caused by ALK rearranged pulmonary adenocarcinoma with pleural and pericardial metastasis, in which, despite a dramatic clinical debut, the correct and timely management of the diagnostic and therapeutic path allowed for extraordinary therapeutic success.