Benign Thyroid Tumours

Most thyroid lumps are benign but 5% are malignant and it is important to distinguish this sinister minority.

Benign thyroid lumps may include:

• Thyroid adenoma
• Thyroiditis
• Thyroid cysts
• Hyperplastic nodules

• Most thyroid nodules are adenomatous. Most are multiple and that is usually shown on ultrasound (US), scintigraphy and at surgery. The nodules are usually non-functioning (cold at scintigraphy), although a few may be hyperfunctioning toxic adenomas (hot on scintigrams). They may also be a hyperfunctioning adenoma in a multinodular goitre.
• When solid, the nodules are poorly encapsulated and not well defined, and they merge into the surrounding tissue. Cystic adenomatous nodules are haemorrhagic, with irregular internal walls and particulate fluid content. Intratumoral calcification is occasionally seen.
• Follicular adenomas are the most common and arise from follicular epithelium. They are usually single, well-encapsulated lesions. On ultrasound adenomas may be hyperechoic or hypoechoic solid nodules with a regular hypoechoic area surrounding ring called the halo sign. Rarely a parathyroid adenoma has an ectopic intrathyroid location.
• Whether solitary adenomas transform into follicular carcinoma is uncertain. In particular, whether aneuploid cells, which are present in approximately 25% of follicular adenomas, represent carcinoma in situ is unclear.
• Follicular adenomas are further classified according to their cellular architecture and relative amounts of cellularity and colloid into fetal (microfollicular), colloid (macrofollicular), embryonal (atypical), and Hürthle (oxyphil) cell types.

About 40% of the general adult population has a single nodule or multiple ones, as shown on ultrasound. Most thyroid nodules are benign.
In most series, 8-65% of patients with clinically normal thyroid glands had one or more grossly visible nodules, whereas the incidence of malignancy was 2-4%.¹

• Most patients with thyroid nodules are asymptomatic, and most nodules are found on clinical examination or self-palpation.
• 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
• Thyroid carcinoma
• Medullary cell carcinoma
• 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

• Perform thyroid function tests. (Most will be euthyroid - refer those which are abnormal for endocrine opinion.²)
• Ultrasound is useful to detect and characterise most thyroid nodules. It can show cystic lesions 2mm wide and solid lesions 3mm wide. Ultrasound examination is far more sensitive than clinical examination and only 4 to 7% of nodules detected by US are clinically palpable.
• Fine needle aspiration (FNA) gives tissue for cytology. It is performed under US guidance (for maximum accuracy) but for palpable nodules it can be performed with palpation. It is safe, inexpensive and provides direct information.
  FNA is best for uninodular lesions.³ 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.^4,5
• Radionuclide imaging looks at iodine uptake by the thyroid:
  • Normal is called "warm".
  • Lesions that take up excessive amounts of iodine are called "hot" - 4% of hot nodules contain tumour.
  • Lesions that do not take up iodine are called "cold" - 16% of cold nodules contain tumour.
  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.
• CT scans and MRI scans are valuable to detect local and mediastinal spread and regional lymph nodes.

General measures

• Solitary benign disease can be observed.
• New thyroid lumps that have been growing over a period of months or patients with a sudden onset of pain in a nodule (which is usually due to a bleed into a cyst) should be referred to a specialist thyroid clinic with provisions for ultrasound and fine needle aspiration assessment, where they should be seen within four weeks of referral.²
• Urgent referral to secondary care is necessary only if the nodule is growing rapidly (over few weeks) or associated with stridor, hoarseness, or cervical lymphadenopathy.²

Pharmacological

• 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.

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.

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.

After exclusion of anaplastic carcinoma, prognosis for thyroid disease is excellent.