Most pneumothoraces are spontaneous (i.e., they occur in the absence of no known pathology and no known lung disease). In addition, pneumothoraces may occur as a result of trauma, inflammation, smoking, and other underlying pulmonary diseases. Certain pulmonary metastases, such as in patients with osteosarcoma, may cause spontaneous pneumothorax especially after chemotherapy. The occurrence of pneumothorax interferes with cancer treatment and increases mortality.