'''Thyroid cancer''' is
cancer of the
thyroid gland. The thyroid concentrates
iodine and so is extremely sensitive to the effects of various radioactive isotopes of iodine produced by
nuclear fission. These radioactive isotopes increase the chances of developing cancer, though thyroid cancer can develop even without any exposure to radioactivity. Some evidence suggests that insufficient or excessive dietary iodine may also increase your risk for thyroid cancer.
Papillary Thyroid Cancer
This is the most common type of thyroid cancer. It occurs more frequently in women and presents in the 30-40year age group. It is also the predominant cancer type in children with thyroid cancer, and in patients with thyroid cancer who have had previous radiation to the head and neck (in this group, the cancer tends to be multifocal with early lymphatic spread, and portends a poor prognosis)
Pathology
- Characteristic Orphan Annie eye nuclear inclusions and psammoma bodies on light microscopy
- Lymphatic spread is more common than hematogenous spread
- Multifocality is common
- The so-called Lateral Aberrant Thyroid is actually lymph node metastasis from papillary thyroid carcinoma.
Prognostic Indicators
AGES - Age, Grade, Extent of disease, Size
AMES - Age, Metastasis, Extent of disease, Size
MACIS - Metastasis, Age at presentation, Completeness of surgical resection, Invasion (extrathyroidal), Size (this is a modification of the AGES system)
TNM - tumor, node, metastasis
Surgical Treatment
- Minimal disease - hemithyroidectomy (or unilateral lobectomy) and isthmectomy is sufficient
- Gross disease - total thyroidectomy
Arguments for Total Thyroidectomy
- Reduced risk of recurrence
- Papillary carcinoma is a multifocal disease (hemithyroidectomy may leave disease in the other lobe)
- Ease of monitoring with thyroglobulin (sensitivity for picking up recurrence is increased in presence of total thyroidectomy)
- Ease of detection of metastatic disease with thyroid scans
Follicular Thyroid Cancer
This occurs more commonly in women of older age group (more than 50 years)
Surgical Treatment
- Unilateral hemithyroidectomy is uncommon due to the aggressive nature of this form of thyroid cancer.
- Total thyroidectomy is almost automatic with this diagnosis. This is invariably followed by radioiodine treatment at levels from 100 to 200 millicuries. Occasionally treatment must be repeated if annual scans indicate remaining tissue.
- Annual thyroid scans consist of withdrawal from thyroxine medication and/or injection of recombinate human Thyroid Stimulating Hormone (TSH). Low dose radioiodine of a few millicuries is administered. Full body nuclear medicine scan follows using a gamma camera.
- Recombinate human TSH, commercial name Thyrogen, is gleaned from the ovaries of geneticly altered hamsters (yes, hamsters).
Hurthle Cell Variant
This type of thyroid cancer is a variant of follicular cell carcinoma with some exceptions
- They are more often bilateral and multifocal
- They are more likely to metastasize to lymph nodes than follicular carcinoma
- Management - like follicular carcinoma, unilateral hemithyroidectomy is performed for non-invasive disease, and total thyroidectomy for invasive disease
Medullary thyroid cancer
This form of thyroid carcinoma originates from the
parafollicular cells (C cells), which produce the hormone
calcitonin. While the increased calcitonin itself is probably not harmful, it is useful as a marker which can be tested in
blood.
Its prognosis is poorer than that of follicular and papillary thyroid cancer. In a proportion, the cancer runs in families, both in isolated form or as part of the syndrome of
multiple endocrine neoplasia (MEN).
Anaplastic thyroid cancer
This form of thyroid cancer has a very poor prognosis due to its aggressive behavior and resistance to cancer treatments. It rapidly invades surrounding tissues (such as the
trachea).
External links
Category:Oncology
Category:Otolaryngology
Category:Endocrinology
it:Tumori della tiroide
pt:Tumores da tiróide