Multifocal mesenchymal hamartoma of the chest wall

: Chest wall hamartomas are extremely rare. Frequently mesenchymal hamartomas are presented as a single mass and contain some primitive mesenchymal elements such as chondroid and trabecular bone structures. A 60‐year‐old man presented to hospital with chest pain. Thirteen years earlier, his CXR and thoracic CT showed three masses on the right and two masses on the left, but he had not received any treatment thereafter. His CT showed the same masses present 13 years earlier, but they were bigger and right thoracotomy was undertaken. At thoracotomy, two sections of the mass in the right posterior mediastinum and one section of the mass in the right apex were excised. They had an occasional bloody appearance and contained small cystic areas, and some areas were extremely hard. Microscopic examination showed that the lesions consisted of mature adipose tissue, a large number of veins of different diameters and collagen tissue. Besides, primitive mesenchymal elements, lymphoid cell accumulations and trabecular bone structures were seen focally. Bilateral chest wall hamartomas are extremely rare and may be confused with malignancy.