Thyroid Lumps

Most thyroid lumps are benign but 5% are malignant and it is important to distinguish this sinister minority. Ultrasound (US) examination is far more sensitive than clinical examination and only 4 to 7% of nodules detected by US are clinically palpable.

Thyroid cancer

• It represents 1.5% of all cancers in adults, 3% of childhood malignancies but 92% of endocrine malignancies.
• 70% of thyroid cancers are papillary, 3 to 10% are medullary or C-cell carcinoma. They originate from the cells that produce calcitonin and the level may be raised. 8 to 16% are anaplastic and usually in the age range 60 to 80 years.
• All the various types of thyroid cancers are 3 to 4 times as common in women as men but with solitary thyroid nodules the risk of malignancy is greater in men.¹
• The risk of malignancy rises with age.

Benign lumps

• About 8% of women and 2% of men have thyroid lumps.
• 95% are benign.
• Thyroid nodules are found in approximately 1.5% of children and adolescents, being 6 times more common in girls than boys.

• Thyroid cancers are more common after exposure to radiation,² with a peak 5 to 30 years later. In the first half of the 20th century, irradiation was used for such conditions as acne, enlarged tonsils and enlarged thymus.
• 7% of survivors of the atomic bombs at Hiroshima and Nagasaki developed thyroid cancer. After the Chernobyl disaster there was a rapid and dramatic increase in papillary carcinoma of thyroid in children in affected countries.³
• Lumps are more common in areas of low iodine consumption and the incidence of malignancy rises from 5% to as high as 40%. Malignancy is more common where benign thyroid disease has existed.
• 10 to 20% of malignancy has a familial component, perhaps with Multiple Endocrine Neoplasia (MEN). This is an autosomal dominant as is familial C-cell carcinoma without MEN.⁴

Probably Benign

• Family history of Hashimoto's disease
• Family history of benign thyroid nodule or goitre
• Symptoms of hyperthyroidism or hypothyroidism
• Pain or tenderness of the nodule
• A soft, smooth, mobile, multi-nodular goitre without one nodule much larger than the rest
• Normal uptake on radio-iodine scan (normal hormone production)
• Simple cyst on ultrasound.

Possibly Malignant

:

• Age less than 20 or above 70
• Male
• Recent onset of swallowing difficulties
• Recent onset of hoarseness
• External neck irradiation during childhood
• Firm, irregular and fixed nodule
• Cervical lymphadenopathy
• Past history of thyroid cancer
• "Cold" nodule on scan ( not making hormone)
• Solid or complex structure on US.

Symptoms

• Thyroid lumps are often asymptomatic and are noticed by family members or seen in the mirror.
• They may sometimes cause pain and rarely present with features of compression of the trachea.
• Ask about previous radiation.

Signs

• Ask the patient to drink some water and note the thyroid move as she swallows.
• Note enlargement or asymmetry.
• Stand behind a seated patient and use the 2nd and 3rd fingers of both hands to examine the gland as she swallows again.
• Note lumps, asymmetry, size and tenderness.
• Check for regional lymphadenopathy.

• Non toxic goitre- non-functioning nodules
• Toxic nodular goitre- functioning nodules
• Graves disease- diffuse overactive thyroid gland
• Hashimoto's disease- autoimmune destruction of the gland
• Solitary thyroid nodule - 15 to 25% are cysts and can be aspirated
• Follicular cell carcinoma
• Medullary cell carcinoma
• Anaplastic carcinoma- older patient. Very malignant
• Thyroid lymphoma- usually non-Hodgkin's
• De Quervain thyroiditis- neck pain, fever, and lethargy soon after an upper respiratory infection or a viral illness
• Acute suppurative thyroiditis- results from bacterial or fungal infection causing abscess.
• Hurthle cell carcinoma.

• Perform thyroid function tests. Most will be euthyroid.
• Ultrasound is useful to detect and characterise most thyroid nodules. It can show cystic lesions 2mm wide and solid lesions 3mm wide.
• Distinguishing functioning toxic nodules and thyroid metastases from follicular and papillary carcinomas is best with ¹²³I uptake studies. ⁶⁷Ga is used in the diagnosis of thyroid lymphoma.
• On radionuclide imaging, lesions that take up excessive amounts of iodine are called "hot" and those that do not take it up are called "cold". Normal is called "warm". 4% of hot nodules contain tumour, compared with 16% of cold nodules. This makes radionuclide imaging unreliable to exclude or confirm cancer. Low ¹²³I uptake in a single palpable nodule gives a risk of malignancy of 10-25%, falling to 1-3% if multiple nodules are demonstrated on the scan.
• About half of papillary carcinomas and a smaller number of follicular carcinomas take up enough iodine in metastases to be detected.
• CT scans and MRI scans are valuable to detect local and mediastinal spread and regional lymph nodes. Fine needle aspiration (FNA) gives tissue for cytology. It is performed under US guidance but for palpable nodules it can be performed with palpation. It is safe, inexpensive and provides direct information.
• FNA is best for uninodular lesions.⁵ Sensitivity is near 80% with specificity approaching 100%. False-negative and false-positive results occur in less than 6%. FNA is the first, and in the vast majority of cases after ultrasound, the only test required for the evaluation of a solitary thyroid nodule.^6,7
• Follicular carcinoma and Hurthle cell carcinoma cannot be diagnosed by FNA. They represent 12% of all thyroid cancers, so these patients with suspicious biopsy need removal of the thyroid lobe with the nodule for histology. Suspicious cytology is reported in 10% of FNA's. They are neither clearly benign nor malignant. 25% are malignant, usually follicular or Hurthle cell cancers. Suspicious aspiration requires surgery.

Multiple endocrine neoplasia (MEN) is associated with medullary carcinoma of the thyroid. Past medical history or family history of pheochromocytoma or hyperparathyroidism should raise the possibility of familial MEN 2a or MEN2b syndrome.

Thyroid lymphomas are almost always non-Hodgkin lymphomas, representing 4-10% of thyroid malignancies. Mainly women over 50 are affected. They often have Hashimoto's thyroiditis. Patients usually present with a rapidly growing mass in the neck, which may cause symptoms of obstruction such as dyspnoea and dysphagia. Thyroid lymphoma arises in a pre-existing chronic thyroiditis with subclinical or overt hypothyroidism in 70 to 80%. The prognosis depends on the stage of the disease at diagnosis. The 5-year survival rate ranges from 89% in early disease to 5% in disseminated disease.

There are a number of histological types that behave differently.

Papillary Carcinoma

It usually presents between 35 and 40 years of age and is 3 times more common in women. It is the commonest form of thyroid cancer. It tends to spread locally in the neck, compressing the trachea and possibly involving the recurrent laryngeal nerve. It can metastasise to lung and bone.

Follicular Carcinoma

This is the second commonest form of thyroid cancer at about 10%. It tends to occur in areas of low iodine. It is 3 times as common in women and tends to strike between 30 and 60 years of age. It may infiltrate the neck as does papillary carcinoma but it has a greater propensity to metastasise and tends to go to lung and bones.

Medullary Cell Carcinoma

This is about 5% of thyroid cancers. About 25% of patients give a family history. Female prepronderance is less marked. The familial form is discussed in the article on multiple endocrine neoplasia. Prophylactic thyroidectomy is advocated for those at risk.

Anaplastic Carcinoma

This represents less than 2% of thyroid cancers. Women are affected more often than men. It tends to strike in the 50s and 60s. Half have metastases at presentation and prognosis is poor.

Thyroid Lymphomas

Between 2 and 5% of thyroid malignancies are lymphomas. They are usually of the non-Hodgkin's lymphoma type.

Hurthle Cell Carcinoma

About 2 to 5% of thyroid cancers are Hurthle cell carcinoma.⁸ They are composed of 75 to 100% Hurthle cells. It is impossible to distinguish benign from malignant tumours on FNA. They do not take up iodine nor respond to TSH. There is a female preponderance. They tend to strike in the 40s and 5 years survival is around 50%.

Non-Drug

Solitary benign disease can be observed.

Drugs

• Biochemical abnormalities of TFTs need to be treated in the usual way. Beta blockers may be needed to control symptoms in some severely toxic patients.
• Patients with benign solitary thyroid nodules may be observed or have suppression therapy with thyroxine. Thyroxine is given for 6-12 months to shrink the nodule. If successful the medication is stopped, with follow-up examination of the thyroid nodule in 3-6 months. If a benign solitary thyroid nodule increases in size, a repeat trial of thyroxine and repeat FNA may be undertaken but growth of a thyroid nodule during therapy is a strong indication for surgery.
• Many endocrinologists no longer recommend thyroid suppression because it produces iatrogenic thyrotoxicosis that is associated with osteoporosis and cardiac arrhythmias. Some maintain a TSH level between 0.1 and 0.3 mU/L to avoid these problems.
• After surgical excision of a cancer, radio-iodine is given 4 to 6 weeks later to ablate any residual tissue. Thyroxine replacement must continue for life. 15 to 20% of cancers respond to TSH, so it should be kept suppressed.
• After thyroid cancer it is common to use tri-iodothyronine (T3) rather than thyroxine(T4). The reason for this is that it has a rather shorter biological life and so it may be stopped for a shorter time to let endogenous TSH rise before doing a ¹³¹I scan for recurrence or metastases.

Surgical

Solitary thyroid nodules that are malignant, suspicious, or indeterminate on FNA require operation. There is much controversy about which operation with advocates for thyroid lobectomy, total or subtotal thyroidectomy.

US guided percutaneous ethanol ablation of thyroid cysts and autonomously functioning nodules is effective with few problems.⁹ Transient pain or a burning sensation at the site of injection may occur.

Both surgery and alcohol injection can cause recurrent laryngeal nerve palsy, which is reported in 1-4% of injections. With alcohol injection it is usually transient with full recovery within 1-3 months. The primary disease can cause nerve damage in both benign and malignant conditions.

This depends upon type and stage but most thyroid cancer has a good prognosis with 90% survival at 10 years, higher in young people without spread.The exception is anaplastic cancer, with a life expectancy of 6 to 12 months and a 5 years survival of 5%.

• Adding iodine to the diet in areas of deficiency will reduce the incidence of both benign and malignant disease.
• In MEN, prophylactic thyroidectomy is performed if the gene is detected.
• Iodine tablets to reduce the risk of subsequent thyroid malignancy are available in case of nuclear accident or explosion of a radioactive device.