Thyroid neoplasm or thyroid cancer generally refers to any of four thyroid malignancies: papillary, follicular, medullary, or anaplastic.Incidence
Thyroid cancer is most common cancer of endocrine system. Estimated number of new cases and deaths from thyroid cancer in 2005:
The prevalence of thyroid nodules in general population is 4-7%, with more nodules in women than in men. The prevalence of thyroid cancer in solitary or multinodular thyroids ranges from 10% to 20%, and prevalence of thyroid cancer in children and older men increases with neck irradiation.
Between 1973 and 1997, incidence of thyroid cancer increased by 24%, while death rate from this type of cancer decreased by 24%.gender
Women suffer more than men (ratio 3:2).age
Most patients are between the ages of 25 and 65 when they are diagnosed with thyroid cancer.geography
The incidence of thyroid cancer is higher in Japan and Hawaii.Causes and risk factors of radiation exposure
Moderate doses of radiation and radiation therapy, which were often used between 1940s and 1960s to treat various benign conditions such as acne in children, enlarged tonsils or thymus, increased risk of developing thyroid cancer, especially nipple cancer. 4% of thyroid cancer patients have a history of neck irradiation.
Recent studies have shown that patients treated with radiation therapy for Hodgkin's disease have an increased risk of developing thyroid cancer compared to general population, although they are more likely to develop hypothyroidism than patients with thyroid cancer.
The time delay between onset of cancer and radiation is on average 20 to 30 years.Genetic factors
Medullary thyroid carcinoma can be sporadic or be a male dominant genetic type II syndrome. Thyroid cancer, including papillary and follicular carcinomas, and breast tumors are also common in Caudwen's multiple hamartoma syndrome. Various oncogenes and tumor suppressor genes are involved in pathogenesis of thyroid tumors.TSH
Patients with chronically elevated TSH levels, such as those with birth defects in thyroid hormone production, may be at an increased risk of developing thyroid cancer.Symptoms and signs Symptoms
On physical examination, a hard or firm and fixed thyroid nodule may indicate cancer. The presence of palpable enlarged nodes in lateral parts of neck, even in absence of palpable nodes in thyroid gland, may indicate metastases to lymph nodes.Diagnostics
Different methods are used to diagnose thyroid cancer. These include: thyroid isotope scan, ultrasound, and fine needle aspiration cytology (FNAC) or biopsy.
An isotopic (nuclear) thyroid scan cannot absolutely distinguish benign from malignant nodules, but it can tell us likelihood of malignancy.
Hot thyroid nodules capable of concentrating radioactive iodine are functional nodules and are unlikely to be malignant. Cold nodules are non-functional lesions that do not enrich isotopes. Most thyroid cancers occur in cold nodules, however, only 10% of cold nodules are malignant.
Ultrasound can detect nodules up to 2 mm in size and helps determine number and size of thyroid nodules.
Nodules with multiple nodes of same size in gland are less likely to be malignant. However, dominant nodules in multinodular glands carry a risk of malignancy compared to true solitary nodules.
Ultrasonography can determine whether a nodule is cystic or solid. Although most hard nodules are benign, thyroid cancer often presents as hard nodules. Cystic nodules or mixed (cystic-solid) lesions are less likely to be carcinoma and more likely to be degenerated colloidal nodules.
Certain features of a hypoechoic nodule increase likelihood of malignancy. These include microcalcifications, central blood flow, or irregular borders.
FNAAC should be used as initial diagnostic test in evaluation of thyroid nodules. The diagnostic accuracy of FNAC cytology is 70–80%.
Sensitivity to palpation increases with size of nodule. The specificity of palpation ranges from 95% to 100%. In studies conducted in specialized centers, reported sensitivity and specificity of FNA varied between 71-95% and 52-99%, respectively.Ultrasound
Ultrasound can detect nodules as small as 2 mm and can be used to determine number and size of thyroid nodules.Isotopic thyroid scan
The thyroid concentrates iodine, so these scans are extremely sensitive to detecting thyroid tissue. An isotope scan of thyroid gland cannot completely distinguish between benign and malignant nodules, but can determine likelihood of malignancy based on functional state of nodules.Aspiration needle cytology
FNA should be used as initial diagnostic test in evaluation of thyroid nodules. First, FNA can determine if a lesion is cystic or solid. For solid lesions, cytology can produce one of three results: benign, malignant, or indeterminate. The diagnostic accuracy of FNA cytology is 70-80%, depending on interpretation of cytological specimens by aspirator and pathologist.Stages and prognostic factors
Thyroid cancer is thyroid cancer. These radioactive isotopes increase chance of developing cancer, although thyroid cancer can develop without radiation exposure.Thyroid cancer stage: too much to repeat here! Thyroid Cancer Treatment
Although there are several types of thyroid cancer, treatment is usually same. Standard treatment includes surgery to remove thyroid gland and any infected lymph nodes. People who have had their thyroid removed must take thyroid hormone pills to replace hormone produced by thyroid gland. Surgery is usually followed by radioactive iodine therapy.
An alternative treatment option based on new research from Mayo Clinic and University of Southern California Keck School of Medicine suggests that radioactive iodine therapy can and should be replaced by TSH (thyroid stimulating hormone) suppression in low-risk patients.