[Ultrastructure and classification of epithelial thymomas]

4 epithelial thymomas out of 36 various types of it were studied electronmicroscopically. The following types were distinguished: clear cell thymoma, dark cell, solid thymoma, lacunar and spindle cell thymoma. These types of thymomas differ not only morphologically, but clinically. Authors suggest, that these tumours take their origin from the star-shaped clear- and dark medullar epithelial cells.