Pleomorphic pulmonary hamartoma: an apparently unique variant of pulmonary hamartoma.

Pulmonary hamartomas of limited variety have been described. Most present as asymptomatic coin lesions in adults and consist of mesenchymal tissue, usually cartilage, in combination with irregular spaces lined by epithelium. Another form is found in the neonate and involves large portions or all of a lung. This is associated with a developmental aberration and is best described as a "congenital adenomatoid malformation". An apparently unique noninvasive tumor mass was resected from the lung of a middle aged man where it was associated with anomalous lung segmentation and the bronchial and blood supply to the lung. The tumor appeared to be undifferentiated by light microscopic criteria. Neurilemoma, leiomyoma, chordoid tumor, mixed tumor, and neurogenic sarcoma all entered the differential diagnosis. Ultrastructural examination demonstrated a highly complex and unique organization. Such a lesion, apparently developmental in this case, should be recognized and carefully distinguished from the malignant mesenchymal, neurogenic, and teratomatous lesions with which it may be confused. Electron microscopy may be helpful in this regard.