Lipomas and Liposarcomas
In contrast to lipomas of soft tissue, lipomas of the lung are distinctly rare. Most are endobronchial and few are parenchymal. About 100 cases have been described up to the mid-1990s. Lipomas occur primarily in men over the age of 40. If sufficiently large a lipoma may cause atelectasis or obstructive pneumonitis. The density of lipomas is about the same as water and this becomes manifest on CT of chest. Microscopically, the main constituent is mature fat. This may be lobulated. Cellular atypia is not commonly seen. As in the case of soft tissue lipomas, lesions with prominent vascular components (angiolipomas) do occur in the lung. One must be careful not to diagnose lipoma in a hamartoma showing an excess of mature fat. One excellent review of lipomas is provided by Moran et al. A unique case of a pulmonary liposarcoma was reported by one of us.