Thyroid tumor — symptoms, diagnosis, treatment

In 2020, thyroid cancer was diagnosed in 586,202 people worldwide. According to the statistics of the Global Cancer Observatory (part of the World Health Organization), in 2030 this number is expected to increase to 680,000 cases. It is most common in older adults, but it can also occur in people under the age of 30.

What is the thyroid gland?

The thyroid gland is an endocrine gland that is responsible for the regulation of metabolism, the body's calcium and phosphorus balance and the production of heat. The primary function of the thyroid gland is to produce thyroid hormones, which are made from iodine and tyrosine.

The scope of the influence of thyroid hormones on the human body is very wide and includes:

• Metabolism;
• Cardiovascular system;
• Development (in children);
• Maintaining sexual function.

The hormones produced by the thyroid gland work by crossing the cell membrane and then binding to the intracellular receptors of thyroid hormones. In this way, a hormonal response takes place and, consequently, the modulation of DNA transcription. In addition, these hormones also affect the cell membrane and the cytoplasm through reactions with enzymes.

What hormones does the thyroid produce?

The thyroid gland is a gland that is responsible for the production of 3 hormones that are extremely important for the body, they are:

• Triiodotrinin (T3) — a thyroid hormone that contains 3 iodine atoms per molecule;
• Thyroxine (T4) — a thyroid hormone that contains 4 iodine atoms per molecule;
• Calcitonin — a peptide hormone.

T3 and T4 hormones are responsible for regulating metabolism and protein synthesis, In children they promote growth and proper development. The secretion of thyroid hormones is regulated by the thyrotropin hormone (TSH), which is produced by the anterior pituitary gland. In turn, TSH is regulated by the thyrotropin-releasing hormone (TRH) produced by the hypothalamus.

Calcitonin is responsible for the proper functioning of the phosphorus-calcium balance by regulating the concentration of calcium in the blood. It acts directly on the bones, inhibits calcium resorption and prevents bone decalcification. Increased concentration of calcium ions in the blood stimulates the thyroid to produce calcitonin.

In order to produce the right amout of hormones, the body requires iodine, which makes up the structure of thyroid hormones. Insufficient iodine supply limits or completely prevents the synthesis of hormones — thus metabolism is slowed down, and the gland becomes enlarged, forming a goiter.

How is the thyroid gland built, and where is it located?

The thyroid gland is located in the middle of the neck. Behind the thyroid are the trachea, larynx, lower pharynx and esophagus. Its structure consists of two lobes — right and left, which are connected by an isthmus. Microscopically the thyroid is formed by vesicles (thyrocytes) containing colloid. The entire gland is surrounded by a thin fibrous sheath — a capsule that has an outer and an inner layer. The latter passes into the gland, creating a septum and dividing the thyroid gland into microscopic lobules. The weight of the adult thyroid gland is about 25 grams, and each lobe is approximately 5 cm long and 3 cm wide. The gland is usually larger in women than in men, and it also becomes enlarged during pregnancy.

Thyroid tumor — symptoms

The most common symptom of thyroid cancer is a bulge in the neck. It is associated with the appearance of a lump. According to a 2018 study by Cosimo Durante, a scientist from Sapienza University of Rome, about 65% of the population has thyroid nodules. Most of them are benign, which qualifies them only for observation. Both initial and long-term follow-up are intended to identify tumors in a small subgroup of lesions that may be clinically significant and may develop into cancer, cause compression, or progress to a functional disease.

In addition, patients who have a thyroid tumor may have the following symptoms:

• Sore throat;
• Hoarseness;
• Swallowing problems;
• Breathing difficulties;
• Enlarged lymph nodes.

After noticing any of the above symptoms, contact your doctor.

Thyroid tumor — causes

It is assumed that the main causes of thyroid cancer are environmental and genetic. The true impact of these factors on the development of thyroid cancer is still being debated

Environmental factors

Environmental factors include exposure to ionizing radiation, both in terms of the natural background radiation as well as other sources (for examplne iatrogenic) basis. Increased incidence is observed in people exposed to radiation from radiotherapy (e.g., treatment of lymphomas) and to the iodine-131 isotope following the Chernobyl and Fukushima nuclear disasters.

Genetic factors

Genetic factors include multiple endocrine neoplasia type 2 (MEN2) as well as familial adenomatous polyposis (FAP). The presence of this mutation in the body is associated with an increased risk of developing the disease. In addition, increased morbidity is observed in people with Cowden, Pendred, Gardner syndrome, and the RET protogen point mutation that occurs in patients with medullary thyroid cancer.

Thyroid tumor — diagnosis

Initial diagnostics include thyroid function tests determining the concentration of specific hormones (TSH, T3, T4) in the blood and ultrasound examination of the tumor (USG). Features such as cystic or spongy structure may suggest that it is a benign lesion that does not require additional testing. On the other hand, an ultrasound image showing a solid, hypoechoic (dark) structure of the tumor, with irregular borders and internal punctate calcifications is worrying and usually warrants a biopsy.

During an ultrasound examination, the size and volume of the thyroid lobes and the width of the isthmus are measured. In the case of an enlarged gland, an assessment is made of its effect on the trachea — whether it compresses it, causing breathing and swallowing problems, and whether it causes enlargement of the neck contour. The assessment of the blood supply to the thyroid tumor also plays an important role in the diagnosis.

The test results allow for risk assessment and help determine whether treatment is necessary. Based on examination results the patient may also be referred for follow up scans. Management of a thyroid tumor may include observation, local treatment, and surgery.

Thyroid tumor — types

Thyroid cancer comes in different varieties. Classifying a given case and determinig the exact type makes it possible to select the best treatment method.

Thyroid adenoma

This is a benign tumor that usually develops in women. It can often be manually palpable and may exert pressure on the larynx, causing hoarseness. Furthermore, it can produce hormones that disrupt homeostasis. A hormonally active adenoma can produce prolactin, growth hormone or corticotropic hormone (ACTH), causing, for example, weight gain. It is the most common cause of hyperthyroidism.

Papillary cancer of the thyroid gland

This is the most common thyroid cancer type — causing around 50% of all thyroid cancer cases. It is more common in young women. Moreover, it grows slowly, and has a good prognosis. Familial adenomatous polyposis and Cowden's syndrome are important risk factors.

Follicular cancer of the thyroid gland

Around 10-20% of thyroid cancer cases are of the follicular type. This type of cancer grows slowly, and the prognosis is quite good. The main risk factor is Cowden's syndrome. In some cases it develops from Hurthle cells (variant). This type of cancer most often metastasizes to the bones and lungs. The new classification also distinguishes non-invasive follicular thyroid carcinoma, the features of which are similar to those of the papillary type.

Medullary thyroid cancer

Makes up about 5-8% of all thyroid cancer cases. It is formed from vesicular cells and can metastasize to distant lymph nodes. It is often seen in patients with type 2 multiple endocrine neoplasia. The prognosis for medullary thyroid carcinoma is uncertain.

Anaplastic thyroid cancer

The rarest type of thyoird cancer, constituting only around 1-2% of all thyroid cancer cases. It is characterized by a very fast growth rate and a poor response to treatment. It metastasizes early and is often accompanied by local infiltration of the trachea. The prognosis for this cancer is unfavorable.

Thyroid tumor — treatment

In most cases, treatment for thyroid cancer involves surgery (thyroidoctomy) to remove the entire gland. If the lesion is characterized by low aggressiveness and small size, it is often possible to perform conserving surgery, which consists of removing the tumor along with a fragment (margin) of healthy tissue surrounding it. This type of treatment is usually reserved for cancers at an early stage. Regardless of the type of surgery, after it is performed, the patient additionally undergoes radiotherapy, chemotherapy or hormone therapy.

Thyroid tumor — prognosis

Prognosis for follicular and papillary cancers is generally better compared to medullary and undifferentiated/poorly differentiated (anaplastic) types. Anaplastic cancers usually grow quickly, demonstrate aggressive local behavior with early distant spread. Luckily this type of cancer is rare. Differentiated neoplasms have a much better prognosis — the cure rate is about 90%. Early detection plays a key role in disease prognosis.