[Intrapulmonary thymoma]

A primary intrapulmonary left-sided thymoma is described in a 23-year old man. Eight similar observations can be found in the world literature. The histology is quite uniform. The tissue shows characteristic epithelial and lymphatic cellular elements but organoid differentiation into medullar and cortex is lacking. Hassall's granules are only rudimentary. Giant cells in all stages of development, tissue mast cells, varied supporting tissue, epithelial border layer and connective tissue capsule are all present. There is no blastomatous degeneration. Theoretical indications to explain the sudden onset of tendency to proliferation of the ectopic thymus independant of age and sex are discussed.