Thyroid and Parathyroid

in the p53 gene result in a protein that lacks this ability, which in turn results in
proliferation of malignant cells. A mutated p53 gene is found in most anaplastic
. thyroid cancers and in thyroid cell lines
Papillary Carcinoma
Papillary carcinoma is the most common of thyroid malignancies, accounting for 80
percent of all thyroid cancers. It is the predominant thyroid cancer in children (75
percent) and in people who were previously exposed to radiation in the neck (85 to 90
percent). Papillary carcinoma occurs more often in women, with a 2:1 female-to-male
. ratio, and the mean age at presentation is 30 to 40 years
Pathology
Papillary thyroid cancers, including mixed papillary follicular carcinoma and the
follicular variant of papillary carcinoma, usually are hard and whitish and remain flat
on sectioning with a blade, rather than bulging as does normal tissue or benign
nodular lesions. Macroscopic calcification, necrosis, or cystic change may be
. apparent. Smaller tumors occasionally may be present inside thyroid cysts
Histologically, papillary carcinomas may exhibit papillary projections, a mixed
pattern (papillary/follicular structures), or a pure follicular pattern with intranuclear
inclusions. The diagnosis is established by characteristic cellular features. Cells are
cuboidal with pale, abundant cytoplasm, crowded nuclei, and intranuclear cytoplasmic
inclusions, the so-called Orphan Annie cells (Fig. 36-23). A characteristic
fibrovascular stroma with calcium deposits (psammoma bodies) may be present.
Tumors that exhibit papillary features such as mixed tumor or the follicular variant of
papillary carcinoma should be classified as papillary carcinomas because they act
biologically as papillary carcinomas. Multifocality in papillary carcinoma is common
(30 to 87.5 percent) and is a minor risk factor in prognosis. Papillary cancers exhibit a
propensity for lymphatic spread within the thyroid and to local lymph nodes
(paratracheal and cervical chain). Papillary tumors may invade local structures such as
the trachea, esophagus, and recurrent laryngeal nerves and rarely are encapsulated.
. Blood-borne metastases usually are a late feature
Macroscopically, there are three recognized forms of papillary thyroid cancer, each
based on the size and extent of the primary disease. Minimal or
occult/microcarcinoma tumors originally included papillary cancers up to 1.5 cm in
diameter. They now are defined as tumors of 1 cm or less in size with no evidence of
local invasiveness through the thyroid capsule and that are not associated with lymph
node metastases. They are nonpalpable and usually are incidental findings at
operative, histologic, or autopsy examination. Studies have demonstrated occult
papillary thyroid cancer to be present in 2 to 36 percent of thyroid glands removed at
autopsy. Recurrence rate in patients with tumors 1.5 cm or smaller after removal is
about 7 percent and the mortality about 0.5 percent. Intrathyroidal tumors are greater
than 1 cm and are confined to the thyroid gland, with no evidence of extrathyroid
invasion. Extrathyroidal tumors are locally advanced with invasion through the
thyroid capsule into adjacent structures. All types of primary thyroid cancers can be
associated with lymph node metastases and invasion into intrathyroidal blood vessels
or occasionally distant metastases. Long-term prognosis is better for intrathyroidal
.
lesions