[Developmental mechanism of the "lung ball"--with reference to the pathological findings of the lung in two resected cases].

The lung ball is a special type of pulmonary aspergillosis (PA) occurring often after chemotherapy for leukemia. Histologically the ball, with air crescent sign on roentgenogram, is compatible with necrotizing lung tissue admixed with Aspergilli. The lung ball differs entirely from the common "fungus ball" in its quality, though they are similar in roentgenological appearances.