Intrathoracic Myxolipoma

Intrathoracic lipomas are quite rare. Yater and Lyddane (1), in reviewing the literature, could find only 11 cases of mediastinal lipoma and reported one of their own. They collected in addition a smaller number of other intrathoracic lipomas which have been repeatedly referred to in the literature on this subject during the last three decades. Fitz (2) concludes that these tumors may arise from fat tissue in the subpleural or mediastinal regions, or at the reflection of the pericardial pleura on the diaphragm, or that a subdiaphragmatic tumor may grow through the diaphragm into the thorax. Several lipomas have been found with an extra- and intrathoracic portion connected by a narrow isthmus through the chest wall or diaphragm, or through a congenital aperture of the sternum, or under the clavicle, appearing as a cervical tumor.

The immediate seriousness of the pressure upon mediastinal structures due to tumors in this region accounts for the relatively small size of these lipomas as compared with the many tumors of 40 pounds or more found in the abdomen and elsewhere, the largest solid tumor of man. However, if the neoplasm is permitted to grow into the pleural cavity without significant pressure upon mediastinal structures it may fill the entire cavity in time, as did the lipoma reported by Leopold (3), which weighed 17 3/8 pounds. Our 19-pound myxolipoma probably grew from the diaphragm or the thoracic wall near the costo-diaphragmatic angle. The earlier roentgenograms (Figs. 1 and 2), taken in May 1929, show a mass in this region which appears to have a capsule over its upper and mesial aspects; however, there was no capsule separating the tumor from mediastinal structures at necropsy.