Distribution of thymic tissue in the mediastinal adipose tissue.

The distribution of thymic tissue in the anterior mediastinal, retrocarinal, and preaortic fat was examined histologically in 27 autopsy subjects. Thymic tissue was found in the anterior mediastinal fat in 12 subjects (44.4%), in the retrocarinal fat in two (7.4%), and in the preaortic fat in none. The finding of ectopic thymic tissue in these areas has not been reported previously, would appear to be surgically inaccessible via a median sternotomy, and may be responsible in part for some of the failures of thymectomy in the treatment of myasthenia gravis.