Intranuclear helioid inclusions.

We have coined the term 'helioid inclusion' to describe a new type of single-membrane-bound intranuclear inclusion which contains one or more rounded bodies with radiating filaments (helioid bodies). Helioid bodies were not found in the rough endoplasmic reticulum in the cytoplasm, or in the cytoplasmic matrix, but a helioid body was seen in dilated rough endoplasmic reticulum included in a double-membrane-bound intranuclear pseudoinclusion. No firm conclusion regarding the genesis of helioid inclusions has emerged from our studies, but two possibilities exist: 1) that helioid bodies derive from modification of serous secretory granules sequestrated in an intranuclear inclusion; or 2) that they develop by condensation of the contents of the perinuclear cistern or rough endoplasmic reticulum subsequent to its sequestration in an intranuclear inclusion.