Hamartomas and other tumor-like malformations of the lungs and heart.

Tumor-like malformative lesions are seen throughout the body, and they may be confused with true neoplasms by clinicians and pathologists alike. In the lungs, they are principally represented by hamartomas-which may contain chondroid, adipocytic, fibroblastic, and myxoid tissue, with entrapped bronchiolar epithelium-and congenital pulmonary airway malformations (CPAMs). The latter have been subdivided into 5 groups, based on their histological features, but they basically comprise proliferations of malformed bronchopulmonary tissues of different types. Type 1 lesions have a capacity for malignant transformation in a small proportion of cases. Malformative cardiac tumefactions include rhabdomyoma-like hamartomas; fibromatous hamartomas; and mesenchymal ventricular hamartomas, which contain cardiac muscle, smooth muscle, fat, vasogenic tissue, and nerves. Another intracardiac proliferation in the same general category is seen in the interatrial septum, in the region of the atrioventricular node. It comprises randomly-disposed gland-like profiles that are made up of endodermal epithelium. Originally thought to be a form of mesothelial lesion, that abnormality is now classified as an endodermal choristoma. All forms of pulmonary and cardiac malformations are only rarely symptomatic, and the necessity for surgical excision of them depends on the particular details of each case.