Ultrastructural study of cylindroma (Poncet-Spiegler tumor).

This report describes the ultrastructural characteristics of a Poncet-Spiegler tumor (cylindroma, turban tumor). This tumor was made up of two cell types and showed a ductal differentiation. Cells bordering duct-like structures were joined together by innumerable desmosomes, especially in places where the cell membranes were markedly invaginated.