The ultrastructure of Bowen's disease: nuclear and nucleolar lesions.

electron microscopic procedures to provide more information on the fine structure of nuclei and nucleoli in giant cells. Nuclei of giant cells were characterized by the presence of an increased number of interchromatinic and perichromatinic granules. In addition, dense globular structures about 500 to 1500 A in diameter were noted in association with chromatin. The spherical clusters observed in interchromatinic areas at the condensed chromatin were composed of particles about 300 A in diameter. Most nucleoli in giant cells were either small and compact or with nucleolonemas. Some small nucleoli of spherical shape were characterized by segregation of fibrillar and granular ribonucleoprotein components. Ring-shaped nucleoli as well as nucleoli with unusual organization of nucleoprotein structures were found only in small numbers. The ultrastructural appearance of nucleoli in some giant cells suggested a low rate or inhibition of the synthesis of nucleolar RNA in these cells.