Abstract
We report an extremely rare case of a synchronous left chest wall and left maxillary sinus chondromesenchymal hamartoma in a toddler female. Although the lesions appeared malignant on imaging, they were benign by biopsy. The enlarging left anterior chest wall mass was surgically resected to prevent cardiovascular compression. The significant chest wall defect was reconstructed using the bird-cage technique with overlying pectoralis major muscle flap and native skin. The lesions at the left posterior rib and left maxillary sinus were closely observed. This case is the first reported synchronous chest wall and maxillary sinus chondromesenchymal hamartoma.