We herein report two cases of appendicitis highlighting it as a rare, possible adverse event of treatment with alectinib.<h4>Case presentation</h4>The first case is a 60-year-old woman with a previous history of stage 1 lobular breast cancer and early-stage lung cancer treated with segmentectomy, subsequently presenting with ALK-positive advanced NSCLC. This evidence concerns the gene ALK and appendicitis.