Key Clinical MessageChildren are more likely to develop Langerhans cell histiocytosis (LCH), a rare disorder with an unknown cause. LCH often invades skeletal systems, while it has occasionally been seen in the sternum or ribs. The best course of treatment for single‐site, skeletal LCH is yet unknown. We present an instance of sternal LCH with adult onset. By fusing and reconstructing chest computed tomography, it was possible to determine the extent of surrounding soft tissue invasion. Because LCH is so uncommon, it could be challenging to recall when we see a sternal lesion. Adult Patients who arrive with anterior chest discomfort and an osteolytic sternal lesion should include LCH on their differential diagnosis list.