Here, we describe two cases of lung metastasis of adamantinoma of long bones, a low-grade bone neoplasm that rarely metastasizes. In both cases, the clinical presentation of the metastases was characterized by spontaneous pneumothorax secondary to tumor cavitation, a phenomenon described in only three of the studies reviewed in the literature. Clinical, radiological, and anatomopathological findings, as well as the procedures adopted in the two cases, are described.