oat cell carcinoma: highly malignant carcinoma composed of small round or egg-shaped cells with little cytoplasm; lung cancers are frequently oat cell carcinomas
malignancy: (medicine) a malignant state; progressive and resistant to treatment and tending to cause death
legionella pneumophilia: the motile aerobic rod-shaped Gram-negative bacterium that thrives in central heating and air conditioning systems and can cause Legionnaires' disease