Helioid inclusions in dedifferentiated acinic cell carcinoma of the parotid gland.

Helioid bodies are exceedingly rare, intranuclear, rounded inclusions with peripheral radiating filaments. These structures, which were formerly observed in only three cases of proliferative breast epithelial lesions, appeared in 0.5-1% of the neoplastic cells of a case of dedifferentiated acinic cell carcinoma of the parotid gland. Helioid bodies are related to rough endoplasmic reticulum cisternae, which suggests that they are the result of the condensation and partial crystallization of their contents when sequestrated into the nuclear compartment of the cell. The presence of helioid bodies may be related to secretory dysfunction of the tumor cells associated with the process of neoplastic dedifferentiation.