Multiple leiomyomas of the lung: benign or malignant.

Primary, unilateral, multiple hamartomas of the lung, observed in a radiograph of the chest, were biopsied and studied by electron microscopy. The ultrastructural findings of dense patches in myofilaments confirmed the pathologic diagnosis made by the conventional light microscopy. Another patient, previously reported to have a leiomyomatous hamartoma, subsequently manifested progressive clinical and radiographic findings suggestive of the ambiguous entity designated as benign metastasizing leiomyoma.