A 28-year-old male with a childhood history of osteopetrosis treated with a stem cell transplantation (SCT) presented with chronic fatigue, malaise, and abdominal pain. CT imaging identified a left lung nodule with osseous, hepatic, and splenic metastases, and diffuse lymphadenopathy. Hepatic biopsy demonstrated metastatic pulmonary adenocarcinoma, ALK-mutated. He received alectinib with an excellent radiographic response maintained a year later. Recipients of a SCT have an increased risk of secondary solid cancer (SSC) and a cumulative incidence of 10-15% by 15-years. Awareness and screening for SSCs are essential for an earlier diagnosis and the possibility of improved outcomes.