Hyalinizing trabecular adenoma of the thyroid gland - Recognition and characterization of its cytoplasmic yellow body

Many round, pale yellow, cytoplasmic inclusion bodies were found in hematox ylin and eosin-stained sections of a hyalinizing trabecular adenoma of the thyroid. The bodies were refractile and frequently had a microvacuolated or granular substructure. They were usually located close to the nucleus, oft en indented it, and rarely occurred within it. Histochemically, they showed a glycosaminoglycan, proteoglycan, and lipid content, displayed autofluore scence on exposure to ultraviolet Light, and were unreactive with a variety of immunostains. Ultrastructurally, the inclusions were consistent with gi ant lysosomes, showing parallel whorled and arrayed membranes ("fingerprint '' bodies) as a component of their substructure. Review of sections of 75 h yalinizing trabecular adenomas in our files revealed that the cytoplasmic b odies were present in all cases (100%), indicating that these inclusions mo st likely are a universal feature of the neoplasm.