Follicular thyroid cancer
Encyclopedia
Follicular thyroid cancer accounts for 15% of thyroid cancer
which occurs more commonly in women of over 50 years old. Thyroglobulin
(Tg) can be used as a tumor marker
for well-differentiated follicular thyroid cancer.
diagnosis. Features sine qua non for the diagnosis of follicular carcinoma are capsular invasion and vascular invasion by tumor cells.
HMGA2
has been proposed as a marker to identify malignant tumors.
Minimally invasive
thyroidectomy has been used in recent years in cases where the nodules are small.
is more productive in finding disease recurrence than full- or whole-body scans
(WBS) using radioactive iodine. However, current protocol (in the USA) suggests a small number of clean annual WBS are required before relying on Tg testing plus neck ultrasound. When needed, whole body scans consist of withdrawal from thyroxine medication and/or injection of recombinant human Thyroid stimulating hormone (TSH). In both cases, a low iodine diet regimen must also be followed to optimize the takeup of the radioactive iodine dose. Low dose radioiodine of a few millicuries is administered. Full body nuclear medicine
scan follows using a gamma camera
. Scan doses of radioactive iodine may be I131
or I123
.
Recombinant human TSH, commercial name Thyrogen, is produced in cell culture from genetically engineered hamster
cells.
thyroid cancer is often considered a variant of follicular cell carcinoma. Hurthle cell forms are more likely than follicular carcinomas to be bilateral and multifocal and to metastasize to lymph nodes. Like follicular carcinoma, unilateral hemithyroidectomy is performed for non-invasive disease, and total thyroidectomy for invasive disease
By overall cancer staging
into stages I to IV, follicular thyroid cancer has a 5-year survival rate of 100% for stages I and II, 71% for stage III, and 50% for stage IV.
, NRAS
, and KRAS
. Also, a chromosomal translocation
specific for follicular thyroid carcinomas is one between paired box gene 8 (PAX-8), a gene important in thyroid development, and the gene encoding peroxisome proliferator-activated receptor γ 1 (PPARγ1), a nuclear hormone receptor contributing to terminal differentiation of cells. The PAX8-PPARγ1 fusion is present in approximately one-third of follicular thyroid carcinomas, specifically those cancers with a t(2;3)(q13;p25) translocation, permitting juxtaposition of portions of both genes. Tumors tend carry either a RAS mutation or a PAX8-PPARγ1 fusion, and only rarely are both genetic abnormalities present in the same case. Thus, follicular thyroid carcinomas seem to arise by two distinct and virtually nonoverlapping molecular pathways.
Thyroid cancer
Thyroid neoplasm is a neoplasm or tumor of the thyroid. It can be a benign tumor such as thyroid adenoma, or it can be a malignant neoplasm , such as papillary, follicular, medullary or anaplastic thyroid cancer. Most patients are 25 to 65 years of age when first diagnosed; women are more affected...
which occurs more commonly in women of over 50 years old. Thyroglobulin
Thyroglobulin
Thyroglobulin is a 660 kDa, dimeric protein produced by and used entirely within the thyroid gland. In earlier literature, Tg was referred to as colloid....
(Tg) can be used as a tumor marker
Tumor marker
A tumor marker is a substance found in the blood, urine, or body tissues that can be elevated in cancer, among other tissue types. There are many different tumor markers, each indicative of a particular disease process, and they are used in oncology to help detect the presence of cancer...
for well-differentiated follicular thyroid cancer.
Classification
It is impossible to distinguish between follicular adenoma and carcinoma on cytological grounds. If fine needle aspiration cytology (FNAC) suggests follicular neoplasm, thyroid lobectomy should be performed to establish the histopathologicalHistopathology
Histopathology refers to the microscopic examination of tissue in order to study the manifestations of disease...
diagnosis. Features sine qua non for the diagnosis of follicular carcinoma are capsular invasion and vascular invasion by tumor cells.
- Follicular carcinoma tends to metastasize to lungLungThe lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
and boneBoneBones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
via the bloodstream. - Papillary thyroid carcinoma commonly metastasizes to cervical lymph nodesCervical lymph nodesCervical lymph nodes are lymph nodes found in the neck.-Classification:There are approximately 300 lymph nodes in the neck, and they can be classified in many different ways.Henri Rouvière produced an influential classification in 1938...
.
HMGA2
HMGA2
High-mobility group AT-hook 2, also known as HMGA2, is a protein that, in humans, is encoded by the HMGA2 gene.- Function :This gene encodes a protein that belongs to the non-histone chromosomal high-mobility group protein family. HMG proteins function as architectural factors and are essential...
has been proposed as a marker to identify malignant tumors.
Initial treatment
- If follicular cells are found on cytological testing, it is common to carry out hemithyroidectomy to distinguish between follicular adenoma and follicular carcinoma on histopathological examination, proceeding to completion thyroidectomy and postoperative radioiodine ablation where carcinoma is confirmed. This way total thyroidectomy is not carried out unnecessarily.
- Thyroidectomy is invariably followed by radioiodine treatment at levels from 50 to 200 millicuries following two weeks of a low iodine diet (LID). Occasionally treatment must be repeated if annual scans indicate remaining cancerous tissue. Some physicians favor administering the maximum safe dose (calculated based on a number of factors), while others favor administering smaller doses, which may still be effective in ablating all thyroid tissue. I-131 is used for ablation of the thyroid tissue.
Minimally invasive
Minimally invasive procedure
There are three main categories which describe the invasiveness of surgical procedures. These are: non-invasive procedures, minimally invasive procedures, and invasive procedures ....
thyroidectomy has been used in recent years in cases where the nodules are small.
Finding disease recurrence
Some studies have shown that thyroglobulin (Tg) testing combined with neck ultrasoundUltrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
is more productive in finding disease recurrence than full- or whole-body scans
Full-body scan
Full-body scan is a scan of the patient's entire body to support the diagnosis and treatment of illnesses. It may also be known as a full-body CT scan if computed tomography technology is used, though there are many types of medical imaging technology which can perform full-body scans .-Use in...
(WBS) using radioactive iodine. However, current protocol (in the USA) suggests a small number of clean annual WBS are required before relying on Tg testing plus neck ultrasound. When needed, whole body scans consist of withdrawal from thyroxine medication and/or injection of recombinant human Thyroid stimulating hormone (TSH). In both cases, a low iodine diet regimen must also be followed to optimize the takeup of the radioactive iodine dose. Low dose radioiodine of a few millicuries is administered. Full body nuclear medicine
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...
scan follows using a gamma camera
Gamma camera
A gamma camera, also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy...
. Scan doses of radioactive iodine may be I131
Iodine-131
Iodine-131 , also called radioiodine , is an important radioisotope of iodine. It has a radioactive decay half-life of about eight days. Its uses are mostly medical and pharmaceutical...
or I123
Iodine-123
Iodine-123 is a radioactive isotope of iodine used in nuclear medicine imaging, including single photon emission computed tomography . The isotope's half-life is 13.22 hours; the decay by electron capture to tellurium-123 emits gamma radiation with predominant energies of 159 keV and 127 keV...
.
Recombinant human TSH, commercial name Thyrogen, is produced in cell culture from genetically engineered hamster
Hamster
Hamsters are rodents belonging to the subfamily Cricetinae. The subfamily contains about 25 species, classified in six or seven genera....
cells.
Hurthle cell variant
Hurthle cellHurthle cell
A Hürthle cell is a cell in the thyroid that is often associated with Hashimoto's thyroiditis as well as follicular thyroid cancer.-Histology:...
thyroid cancer is often considered a variant of follicular cell carcinoma. Hurthle cell forms are more likely than follicular carcinomas to be bilateral and multifocal and to metastasize to lymph nodes. Like follicular carcinoma, unilateral hemithyroidectomy is performed for non-invasive disease, and total thyroidectomy for invasive disease
Prognosis
The overall 5-year survival rate for follicular thyroid cancer is 91%, and the 10-year survival rate is 85%.By overall cancer staging
Cancer staging
The stage of a cancer is a description of the extent the cancer has spread. The stage often takes into account the size of a tumor, how deeply it has penetrated, whether it has invaded adjacent organs, how many lymph nodes it has metastasized to , and whether it has spread to distant organs...
into stages I to IV, follicular thyroid cancer has a 5-year survival rate of 100% for stages I and II, 71% for stage III, and 50% for stage IV.
Associated mutations
Approximately one-half of follicular thyroid carcinomas have mutations in the Ras subfamily of oncogenes, most notably HRASHRAS
GTPase HRas also known as transforming protein p21 is an enzyme that in humans is encoded by the HRAS gene. The HRAS gene is located on the short arm of chromosome 11 at position 15.5, from base pair 522,241 to base pair 525,549.- Function :...
, NRAS
NRAS
NRAS can be*Neuroblastoma RAS viral oncogene homolog*Australian National Rental Affordability Scheme...
, and KRAS
KRAS
GTPase KRas also known as V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog and KRAS, is a protein that in humans is encoded by the KRAS gene. Like other members of the Ras family, the KRAS protein is a GTPase and is an early player in many signal transduction pathways...
. Also, a chromosomal translocation
Chromosomal translocation
In genetics, a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes. A gene fusion may be created when the translocation joins two otherwise separated genes, the occurrence of which is common in cancer. It is detected on...
specific for follicular thyroid carcinomas is one between paired box gene 8 (PAX-8), a gene important in thyroid development, and the gene encoding peroxisome proliferator-activated receptor γ 1 (PPARγ1), a nuclear hormone receptor contributing to terminal differentiation of cells. The PAX8-PPARγ1 fusion is present in approximately one-third of follicular thyroid carcinomas, specifically those cancers with a t(2;3)(q13;p25) translocation, permitting juxtaposition of portions of both genes. Tumors tend carry either a RAS mutation or a PAX8-PPARγ1 fusion, and only rarely are both genetic abnormalities present in the same case. Thus, follicular thyroid carcinomas seem to arise by two distinct and virtually nonoverlapping molecular pathways.