The natural history of idiopathic pulmonary fibrosis is characterized by a slow progression resulting in respiratory failure and death. The progression to the fulminant form is rapid in a small percentage of cases, however. Within weeks or months, patients develop respiratory distress, and extensive ground-glass patterns can be seen in computed tomography scans and hyaline membranes in biopsy samples. This is described as an accelerated phase of idiopathic pulmonary fibrosis, in which elevated levels of acute-phase reactants and tumor markers have been reported. To date, the monoclonal tumor marker, CA 15/3 has not been associated with the accelerated phase.