Mesenchymal hamartoma of the chest wall in a 10-year-old girl mimicking malignancy: a case report.

We herein report a rare case of mesenchymal hamartoma of the chest wall in a 10-year-old girl. She complained of chest pain and was diagnosed with a large chest wall tumor originating from the left fourth rib. Malignancy such as osteosarcoma or chondrosarcoma could not be ruled out with imaging studies. Therefore, we performed a core needle biopsy assisted by thoracoscopy, which revealed no malignancy. Therefore, extended resection with chest wall reconstruction was unnecessary, and thoracoscopy-assisted tumor excision with only the removal of the involved fourth rib was performed without chest wall reconstruction. The postoperative course was satisfactory with no thoracic deformity and no recurrence.