Autonomic nerve tumour with skeinoid fibres: ultrastructure of skeinoid fibres examined by quick-freezing and deep-etching method.

A case of gastrointestinal autonomic nerve tumour with skeinoid fibres (SFs) of the jejunum in a 79-year-old Japanese man, was examined by the quick-freezing and deep-etching (QF-DE) method. The tumour consisted of spindle cells with immunohistochemical reactions for vimentin, NSE and CD34. Electron microscopically, features of the neural cells of the myenteric plexus were observed. The QF-DE method demonstrated intercellular meshwork structures, consisting of thin filaments (7-15 nm), with granular deposits. Fully developed parts of the deposits formed nodular aggregates composed of irregularly surfaced thick fibrils (30-48 nm) with a tendency to linear arrangement (SFs). We detected many interconnecting thin filaments (ICTFs) between the SFs, which were pre-existing components in the meshwork, avoiding the granular deposits. The focal thickening formed by the connection between SFs and ICTFs revealed a periodicity typical of SFs (33-45 nm). We conclude that SFs are formed by decoration of the granular deposits along pre-existing intercellular meshwork structures.