Thyroid neoplasm or
thyroid cancer usually refers to any of four kinds of
malignantCancer is a class of diseases in which a group of cells display uncontrolled growth , invasion , and sometimes metastasis...
tumorA tumor or tumour is the name for a swelling or lesion formed by an abnormal growth of cells . Tumor is not synonymous with cancer. A tumor can be benign, pre-malignant or malignant, whereas cancer is by definition malignant....
s of the
thyroidThe thyroid is one of the largest endocrine glands in the body. This gland is found in the neck inferior to the thyroid cartilage and at approximately the same level as the cricoid cartilage...
gland:
papillaryPapillary thyroid cancer is the most common type of thyroid cancer. It occurs more frequently in women and presents in the 30-40 year age group...
,
follicularFollicular thyroid cancer is a form of thyroid cancer which occurs more commonly in women of over 50 years old. Thyroglobulin can be used as a tumor marker for well-differentiated follicular thyroid cancer.-Classification:...
,
medullaryMedullary thyroid cancer is a form of thyroid carcinoma which originates from the parafollicular cells , which produce the hormone calcitonin....
or
anaplasticAnaplastic thyroid cancer is a form of thyroid cancer which has a very poor prognosis due to its aggressive behavior and resistance to cancer treatments.-Presentation:...
. Most patients are 25 to 65 years of age when first diagnosed; women are more affected than men. Papillary and follicular tumors are the most common. They grow slowly and may recur, but are generally not fatal in patients under 45 years of age. Medullary tumors have a good prognosis if restricted to the thyroid gland and a poorer prognosis if
metastasisMetastasis , or metastatic disease, sometimes abbreviated mets, is the spread of a disease from one organ or part to another non-adjacent organ or part...
occurs. Anaplastic tumors are fast-growing and respond poorly to therapy.
Thyroid nodule-Presentation:Often these abnormal growths of thyroid tissue are located at the edge of the thyroid gland so they can be felt as a lump in the throat. When they are large or when they occur in very thin individuals, they can even sometimes be seen as a lump in the front of the...
s are diagnosed by ultrasound guided fine needle aspiration (USG/FNA) or frequently by
thyroidectomyA thyroidectomy is an operation that involves the surgical removal of all or part of the thyroid gland. Surgeons often perform a thyroidectomy when a patient has thyroid cancer or some other condition of the thyroid gland...
(surgical removal and subsequent histological examination). As thyroid cancer can take up
iodineIodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
, radioactive iodine is commonly used to treat thyroid carcinomas, followed by
TSHThyroid-stimulating hormone is a peptide hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland which regulates the endocrine function of the thyroid gland....
suppression by high-dose
thyroxineThyroxine, or 3,5,3',5'-tetraiodothyronine , a form of thyroid hormones is the major hormone secreted by the follicular cells of the thyroid gland. Thyroxine is synthesized via the iodination and covalent bonding of the phenyl portions of tyrosine residues found in an initial peptide,...
therapy.
Symptoms
Most often the first symptom of thyroid cancer is a nodule in the thyroid region of the neck. However, many adults have small nodules in their thyroids. But typically under 5% of these nodules are found to be malignant. Sometimes the first sign is an enlarged lymph node. Later symptoms that can be present are pain in the anterior region of the neck and changes in voice.
Thyroid cancer is usually found in a
euthyroidThe state of having normal thyroid gland function. Examples of a nonfunctioning thyroid gland may be hypothyroidism, hyperthyroidism, or thyroiditis....
patient, but symptoms of
hyperthyroidismHyperthyroidism is the term for overactive tissue within the thyroid gland,resulting in overproduction and thus an excess of circulating free thyroid hormones: thyroxine , triiodothyronine , or both...
or
hypothyroidismHypothyroidism is the disease state in humans and in animals caused by insufficient production of thyroid hormone by the thyroid gland. Cretinism is a form of hypothyroidism found in infants.-Causes:...
may be associated with a large or metastatic well-differentiated tumor.
Nodules are of particular concern when they are found in those under the age of 20. The presentation of benign nodules at this age is less likely, and thus the potential for malignancy is far greater.
Diagnosis
After a
noduleNodule may refer to:*Nodule , a small knobbly rock or mineral cluster, such as a manganese nodule*Nodule , a small aggregation of cells*Nodule , a lesion similar to a papule...
is found during a physical examination, a referral to an endocrinologist, a
thyroidologistA thyroidologist is a medical practitioner specializing in the thyroid and related areas.In the United States it refers to a board certified endocrinologist physician, who is either a full time academician with multiple responsibilities beside thyroid patient care, or a clinical thyroidologist...
or otolaryngologist may occur. Most commonly an
ultrasoundUltrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Although this limit varies from person to person, it is approximately 20 kilohertz in healthy, young adults and thus, 20 kHz serves as a useful lower limit in describing ultrasound...
is performed to confirm the presence of a nodule, and assess the status of the whole gland. Measurement of thyroid stimulating hormone and anti-thyroid antibodies will help decide if there is a functional thyroid disease such as
Hashimoto's thyroiditisHashimoto's thyroiditis or chronic lymphocytic thyroiditis is an autoimmune disease where the body's own T-cells attack the cells of the thyroid. It was the first disease to be recognised as an autoimmune disease....
present, a known cause of a benign nodular goiter.
Fine needle biopsy
One approach used to determine whether the nodule is malignant is the fine needle biopsy (FNB), which some have described as the most cost-effective, sensitive and accurate test.
FNB or ultrasound-guided FNA usually yields sufficient thyroid cells to assess the risk of malignancy, although in some cases, the suspected nodule may need to be removed surgically for pathological examination.
Rarely, a biopsy is done using a large cutting needle, so that a piece of nodule capsule can be obtained.
Blood tests
Blood or imaging tests may be done prior to or in lieu of a biopsy. The possibility of a nodule which secretes thyroid hormone (which is less likely to be cancer) or hypothyroidism is investigated by measuring thyroid stimulating hormone (TSH), and the thyroid hormones
thyroxineThyroxine, or 3,5,3',5'-tetraiodothyronine , a form of thyroid hormones is the major hormone secreted by the follicular cells of the thyroid gland. Thyroxine is synthesized via the iodination and covalent bonding of the phenyl portions of tyrosine residues found in an initial peptide,...
(T4) and
triiodothyronineTriiodothyronine, C
15H
12I
3NO
4, also known as T
3, is a thyroid hormone.Thyroid-stimulating hormone activates the production of thyroxine and T
3. This process is under regulation. In the thyroid, T
4 is converted to...
(T3).
Tests for serum thyroid autoantibodies are sometimes done as these may indicate autoimmune thyroid disease (which can mimic nodular disease).
Imaging
The blood assays may be accompanied by
ultrasoundDiagnostic sonography is an ultrasound-based diagnostic imaging technique used to visualize subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions. Obstetric sonography is commonly used during pregnancy and is widely...
imaging of the nodule to determine the position, size and texture, and to assess whether the nodule may be
cystA cyst is a closed sac having a distinct membrane and division on the nearby tissue. It may contain air, fluids, or semi-solid material. A collection of pus is called an abscess, not a cyst. Once formed, a cyst could go away on its own or may have to be removed through surgery.- Locations :*Acne...
ic (fluid filled). Also suspicious findings in a nodule are hypoechoic, irregular borders,
microcalcificationMicrocalcifications are tiny specks of mineral deposits , that can be scattered throughout the mammary gland, or occur in clusters. When found on a mammogram, a radiologist will then decide whether the specks are of concern - usually, this is not the case...
s, or very high levels of blood flow within the nodule. Less suspicious findings in benign nodules include, hyperechoic, comet tail artifacts from
colloidA colloid is a type of chemical mixture in which one substance is dispersed evenly throughout another.The particles of the dispersed substance are only suspended in the mixture, unlike in a solution, in which they are completely dissolved...
, no blood flow in the nodule and a
haloA halo is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
, or smooth border.
Some clinicians will also request
technetiumTechnetium is the lightest chemical element with no stable isotope, and is therefore the lightest radioactive element. It has atomic number 43 and symbol Tc. Technetium occurs in nature only in minute amounts; as a spontaneous fission product in uranium ore or by neutron capture in molybdenum...
(Tc) or radioactive
iodineIodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
(I) imaging of the thyroid. An
123I scan showing a hot nodule, accompanied by a lower than normal TSH, is strong evidence that the nodule is not cancerous.
Classification
Thyroid cancers can be classified according to their pathological characteristics. The following variants can be distinguished (distribution over various subtypes may show regional variation):
- Papillary thyroid cancer
Papillary thyroid cancer is the most common type of thyroid cancer. It occurs more frequently in women and presents in the 30-40 year age group...
Up to 75% - often in young females - excellent prognosis
- Follicular thyroid cancer
Follicular thyroid cancer is a form of thyroid cancer which occurs more commonly in women of over 50 years old. Thyroglobulin can be used as a tumor marker for well-differentiated follicular thyroid cancer.-Classification:...
Up to 15%
- Medullary thyroid cancer
Medullary thyroid cancer is a form of thyroid carcinoma which originates from the parafollicular cells , which produce the hormone calcitonin....
(Up to 8%)- cancer of the parafollicular cells, part of MEN-2.
- Anaplastic thyroid cancer
Anaplastic thyroid cancer is a form of thyroid cancer which has a very poor prognosis due to its aggressive behavior and resistance to cancer treatments.-Presentation:...
Less than 5%. It is not responsive to treatment and can cause pressure symptoms.
- Others
- Lymphoma
Lymphoma is a cancer that begins in the lymphocytes of the immune system and presents as a solid tumor of lymphoid cells. They often originate like balls in lymph nodes, presenting as an enlargement of the node...
- Squamous cell carcinoma
In medicine, squamous cell carcinoma is a form of cancer of the carcinoma type that may occur in many different organs, including the skin, lips, mouth, esophagus, urinary bladder, prostate, lungs, vagina, and cervix...
, sarcomaA sarcoma is a cancer of the connective tissue resulting in mesoderm proliferation.This is in contrast to carcinomas, which are of epithelial origin...
The follicular and papillary types together can be classified as "differentiated thyroid cancer". These types have a more favorable prognosis than the medullary and undifferentiated types.
- Papillary microcarcinoma is a subset of papillary thyroid cancer defined as measuring less than or equal to 1cm. . The highest incidence of papillary thyroid microcarcinoma in autopsy series was reported by Harach et al. in 1985, who found 36 of 101 consecutive autopsies were found to have an incidental microcarcinoma . Michael Pakdaman et al. report the highest incidence in a retrospective surgical series at 49.9% of 860 cases . Management strategies for incidental papillary microcarcinoma on ultrasound (and confirmed on FNAB) range from total thyroidectomy with radioactive iodine ablation to observation alone. Harach et al. suggest using the term "occult papillary tumor" to avoid giving patients distress over having cancer.It was Woolner et al. who first arbitrarily coined the term "occult papillary carcinoma" in 1960, to describe papillary carcinomas ≤ 1.5cm in diameter.
Thyroid adenomaA thyroid adenoma is a benign tumor of the thyroid gland.Almost all thyroid adenomas are follicular adenomas. Follicular adenomas can be described as "cold"...
is a benign neoplasm of the thyroid.
Etiology
From the 1940s to 1960s, external, low-dose radiation to the head and neck during infancy and childhood was used to treat many benign diseases. This type of therapy has been shown to predispose persons to thyroid cancer. The younger the patient was at time of exposure, the higher the risk of developing cancer.
Another cause may be due to high-dose irradiation to the head and neck. Patients with Hodgkin lymphoma treated with mantlefield irradiation have an increased risk of developing thyroid cancer, although hypothyroidism is more likely.
Treatment
If the nodule is benign, patients may receive thyroxine therapy to supress
thyroid-stimulating hormoneThyroid-stimulating hormone is a peptide hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland which regulates the endocrine function of the thyroid gland....
and should be reevaluated in 6 months.
If the nodule is malignant or has indeterminate cytologic features, it may require surgery. Common surgeries include
thyroidectomyA thyroidectomy is an operation that involves the surgical removal of all or part of the thyroid gland. Surgeons often perform a thyroidectomy when a patient has thyroid cancer or some other condition of the thyroid gland...
,
lobectomyLobectomy means surgical excision of a lobe. This may refer to a lobe of the lung, a lobe of the thyroid , or a lobe of the brain ....
, and tracheostomy.
Radioactive
Iodine-131Iodine-131 , also called radioiodine, is a radioisotope of iodine which has medical and pharmaceutical uses. It is also a radioactive hazard and was a significant contributor to the health effects of the Chernobyl disaster....
is used in patients with papillary or follicular thyroid cancer for ablation of residual thyroid tissue after surgery and for the treatment of thyroid cancer. Patients with medullary, anaplastic, and most Hurthle cell cancers do not benefit from this therapy.
External irradiation may be used when the cancer is unresectable, when it recurs after resection, or to relieve pain from bone metastasis.
See also
- radioactive contamination
Radioactive contamination is the uncontrolled distribution of radioactive material in a given environment. The amount of radioactive material released in an accident is called the source term.- Sources of contamination :...
(a cause of thyroid cancer)
- http://en.wikipedia.org/wiki/Papillary_thyroid_cancer
External links