Thyroid Cancer Pathology
Papillary cancer is the most common thyroid malignancy (85%). It most commonly occurs in women of the third to fifth decade. However, it also occurs in children. Papillary cancer is importantly associated with radiation exposure confirmed by the epidemic of thyroid cancer in children and babies following the Chernobyl nuclear power station disaster [1, 2]. It is derived from the follicular epithelium and has a papillary growth pattern with psammoma bodies and characteristic nuclear changes that can be diagnosed on cytology. These include Orphan Annie nuclei, intranuclear inclusions of cytoplasm and nuclear grooves although inclusions and nuclear grooves can be seen in Hashimoto’s disease . Papillary cancers invade the lymphatics resulting in multifocality and lymph node metastases. Venous invasion is less commonly seen (5–7%) causing lung and bone metastases . There are many variants to the classic papillary cancer, some of which are known to have more aggressive behaviour including tall cell variant, columnar cell variant and diffuse sclerotic type and in stratifications are usually categorised into high-risk groups. There are two more categories that require further discussion.
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