Brigatinib in Pediatric and Young Adult Patients With ALK+ ALCL, IMT or Other Solid Tumors

This study is testing brigatinib (an ALK inhibitor targeted therapy) in children and young adults up to age 26 with cancers that have a specific genetic change in the ALK gene, including a type of lymphoma called ALK+ ALCL, inflammatory myofibroblastic tumors (IMT), and other solid tumors. **You may be eligible if:** - You are between 1 and under 26 years old and can swallow tablets - You have a confirmed diagnosis of cancer with an activating ALK genetic alteration - Your cancer has relapsed, is not responding to standard therapy, or cannot be surgically removed without severe consequences - Your performance status and organ function meet the required thresholds - You have not previously taken brigatinib (other ALK inhibitors are allowed) **You may NOT be eligible if:** - You are currently taking strong medications that interact with brigatinib - You have another concurrent primary cancer - You have significant heart problems (recent heart attack, heart block, or uncontrolled high blood pressure) - You have active hepatitis B, C, or HIV - You have conditions affecting drug absorption from the gut - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.