Thyroid Cancer

Overview

Thyroid cancer is a relatively rare form of cancer involving the thyroid gland. It accounts for only about 1.5% of new cancer diagnoses in the US; however, over the last three decades, the incidence of thyroid cancer has been steadily increasing. Thyroid cancer is the fastest increasing malignancy in both men and women. The incidence of thyroid cancer has more than doubled since 1990 and it is projected that by 2030, thyroid cancer will replace colorectal cancer as the fourth leading cancer diagnosis. This rise has been largely attributed to more frequent detection as the highest increase is seen in the small occult tumors. 

Physical exam and ultrasound are the primary tools to evaluate the thyroid gland; while blood tests have limited utility. Suspicious masses in the thyroid can be readily sampled or biopsied with a small needle. Some cancers of the thyroid are hard to differentiate from non-cancerous changes based on this needle biopsy and may ultimately require surgical removal of all or part of the gland in order to properly diagnose the presence of thyroid cancer. 

There are four subtypes of cancer that arise from the thyroid gland itself. In addition, rarely lymphoma or cancers from other areas in the body can spread to the thyroid gland. More than 80% of thyroid cancers are papillary. This is generally a low grade, slowly spreading cancer that is often successfully removed with surgery. Additional treatment is sometimes indicated depending on the extent and characteristics of the tumor. Lymph node removal and or administration of radio-iodine to treat residual microscopic disease are among these therapies. Follicular cancer represents about 10% of primary thyroid cancers and can spread to others areas in the body in about 10-30% of patients. Treatment is generally limited to surgical removal of the thyroid. Medullary cancer, which can be hereditary accounts for less than 10% of thyroid cancers and can be associated with other abnormalities of the endocrine system. Anaplastic cancer is a very rare form that generally occurs in older patients. Treatment involves radiation, chemotherapy and surgery. As with most cancers, a team of specialists are usually involved in diagnosis and comprehensive treatment of thyroid cancer. The goal is to eradicate the cancer and minimize the risk of recurrence.

 

Causes

There are certain risk factors such as a history of neck irradiation, exposure to external sources of radiation and a family history of thyroid cancer that are associated with thyroid cancer.

Symptoms

A thyroid nodule is any abnormal growth of thyroid tissue into a lump. It is often diagnosed on clinical examination or noted on ultrasound. The nodule can be solid or fluid-filled (cyst), solitary or multiple. The vast majority of thyroid nodules are benign, but some can harbor thyroid cancer (<10%). Furthermore, most thyroid nodules are asymptomatic but others can cause symptoms based on size, location and excessive thyroid hormone production. Depending on its size or characteristics, some nodules will require a biopsy. This is often accomplished by first numbing the skin overlying the nodules and then obtaining some sample cells with a small needle. This procedure is minimally invasive and is often performed under the guidance of ultrasound to increase the accuracy. The result of the biopsy will guide further management.

Treatments

Treatment most often includes a combination of surgery, radioiodine therapy and hormone replacement therapy. With appropriate treatment, patients with small early detected tumors can have excellent long term survival. Patients that succumb to this disease typically suffer from rare subsets of the malignancy including anaplastic and medullary carcinoma.