previous exposure to ionizing radiation
they may be well circumscribed and even encapsulated; in other instances, they infiltrate the adjacent parenchyma with ill-defined margins
areas of fibrosis and calcification and are often cystic
Gross papillary foci may be present
Unlike hyperplastic papillary lesions, the neoplastic papillae have dense fibrovascular cores. Concentrically calcified structures termed psammoma bodies are often present within the papillae
nuclear features even in the absence of a papillary architecture are diagnostic of papillary Ca- finely dispersed chromatin, which imparts an optically clear appearance, giving rise to the designation "ground-glass" or "Orphan Annie eye" nuclei
Invaginations of the cytoplasm may give the appearance of intranuclear inclusions (hence the term pseudo-inclusions)
Metastases to adjacent cervical lymph nodes common- might be the only presentation of the neoplasm.