Lung adenocarcinoma with type II pneumocyte characteristics.

We report a case of primary lung adenocarcinoma with type II pneumocyte characteristics. Electron microscopic examination demonstrated that the tumour cells had well-developed microvilli and cytoplasmic lamellar inclusion bodies. These ultrastructural features are similar to those seen in type II pneumocytes of normal lung tissue. Western blot analysis, using monoclonal antibody against human surfactant protein A (SP-A), clearly demonstrated that the tumour cells expressed human SP-A, which is a major pulmonary surfactant protein produced by type II pneumocytes. These observations suggest that the tumour was derived from a type II pneumocyte.