Papillary Carcinoma of the Thyroid

Occur at any age and rarely has been diagnosed as a congenital tumor.
Most in the third and fifth decades .
Women are affected more than men in ratios of 2:1 to 4:1 .
Etiologic factors for papillary carcinoma are not well established.
External radiation probably plays a role in the development of papillary cancer.

Glandular lymphatics invasion ->  Regional node metastases (extremely common (50% or more)) and multifocal tumors within the same gland.
Venous invasion rarely occurs.
Metastases outside the neck are unusual (5%–7% of cases).

Gross
Firm and usually white in color with an invasive appearance. Lesional calcification is a common feature.
Maybe extensive sclerosis, the lesion may resemble a scar.
Rarely be completely cystic, making diagnosis difficult.
Necrosis (in the absence of a prior needle biopsy) is not a feature of typical papillary carcinoma and suggests a higher-grade lesion.

Microscopic
Neoplastic papilla contain a central core of fibrovascular (occasionally just fibrous) tissue.
Crowded oval nuclei <-> basal round and uniform nuclei
Nuclear clearing, ground glass, elongation, and overlapping, occasional grooves = intranuclear inclusions of cytoplasm.
Psammoma bodies that represent the "ghosts" of dead papillae. (Progressive infarction of the papilla and ensuing calcium deposition lead to lamellation)

But
Cleared nuclei : papillary carcinoma, autoimmune thyroiditis, particularly Hashimoto disease.
Nuclear grooves : Hashimoto disease, adenomatous hyperplasia, and diffuse hyperplasia, follicular adenomas (particularly hyalinizing trabecular adenoma).

Pitful
Nodal metastasis will involve one node that may be cystic.
Nodal metastases in papillary cancer may appear papillary, mixed, or follicular.
Focus of epithelial cells in lymph node maybe metastatic thyroid carcinoma.

Variant:
Follicular Variant ---
greater risk to metastasize outside the neck and for vascular invasion;
regional nodal metastases are less common than in classic papillary cancer.
Papillary Microcarcinoma ---
WHO, papillary microcarcinoma is defined as tumor measuring 1 cm or less.
Tall Cell Variant ---
Columnar Cell Variant ---

Prognosis:
Regional lymph node metastases not adversely affect long-term prognosis.
Poor prognostic factors : older age at diagnosis, male sex, large tumor size, and extrathyroidal growth.

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