Intranuclear Helioid Inclusions in a Case of Breast Carcinoma.

Helioid inclusions are single membrane-bounded intranuclear bodies of unknown nature which have been described in a case of breast adenoma, in mammary hyperplasia, and in a case of acinic cell carcinoma of the parotid gland. We report the detection of helioid inclusions in a case of breast carcinoma, which involves a 60-year-old woman with infiltrating ductal breast carcinoma of apocrine type. On electron microscopic examination we observed characteristic intranuclear helioid inclusions in some carcinoma cells. Occasionally intranuclear profiles of dense granules were present, some of which showed a just discernible filamentous border. The significance of these rare ultrastructural inclusions remains to be elucidated.