Papillary Thyroid Cancer (PTC): Overview

Thyroid carcinoma comprises 1% of all malignancies but is the commonest malignant endocrine tumour. Annual incidence in the UK is reported at 2.3 per 100,000 women and 0.9 per 100,000 men (1).

Papillary thyroid carcinoma is the most common comprising 80% of all thyroid malignancies. It occurs in all age groups but is most common in the 3rd to 5th decades (2). Whilst, lymph node metastases are often present at diagnosis, haematogenous spread is a rare and late event. In contrast, distant metastases (commonly to bone and lung) are more common in follicular thyroid carcinoma, which represents approximately 10–20% of all thyroid cancers (2).

Distant metastases are noted in 1-3% of patients with thyroid cancer at initial diagnosis whereas 7-23% develop distant metastases during the course of the disease process (3). Commonly, thyroid carcinoma presents as a neck lump (which may be clinically solitary or multinodular) and initial presentation in the form of bone metastases leading to the diagnoses of thyroid carcinoma is rare.

Thyroid carcinoma is rare comprising 1% of all malignancies and commonly presents as a neck lump. Papillary thyroid carcinoma unlike follicular thyroid carcinoma tends not to metastasise to distant sites.

We present a case of papillary thyroid carcinoma presenting as a solitary asymptomatic pelvic bone metastases and highlight current management of bone metastases. A 59-year old female was found on abdominal computerised tomography to have an incidental finding of a 4.5 cm soft tissue mass in the right iliac bone. Biopsy of the lesion confirmed metastatic thyroid carcinoma. There was no history of a neck lump, head and neck examination was normal. Further imaging confirmed focal activity in the right lobe of the thyroid. A total thyroidectomy and level VI neck dissection was performed and histology confirmed follicular variant of papillary carcinoma.

Early detection of bone metastases have been shown to improve prognosis and thyroid carcinoma should be considered as a potential primary malignancy.

PTC Symptoms

Most patients with thyroid cancer do not have any symptoms. Typically, patients present with a thyroid nodule that is found to be cancer on further evaluation. As with all thyroid disease, a thorough history is important, such as a family history of thyroid cancer, personal history of radiation exposure, or enlarged lymph nodes. Your physician will review with you any symptoms such as pain, swelling in the neck, difficulty with swallowing, shortness of breath, difficulty with breathing or changes in your voice. If the nodule is large, it may cause symptoms such as difficulty swallowing, choking sensations, or a large mass in the neck. Rarely, the cancer can grow into the nerves (i.e. the recurrent laryngeal nerves) that control the voicebox and cause hoarseness.

Risk factors for PTC

For most patients, we do not know the specific reason why they develop thyroid cancer, though it does appear to be more common in women, and is definitely seen in younger patients as well. It is important to note that some patients with multiple risk factors never develop thyroid cancer. In fact, most people who have thyroid cancer, have no obvious known risk factor. Known risk factors for papillary thyroid cancer include:

Radiation exposure
Papillary thyroid cancer is more common in people who have a history of exposure to significant ionizing radiation. Radiation induced thyroid cancer can happen at anytime between a few years after exposure to as long as 30 to 50 years later. Radiation exposure is broken down into three major categories:

Childhood exposure
X-ray treatments were widely used in the 1940s and 1950s. This radiation was used to treat acne, enlarged tonsils, lymphomas, ringworm, enlarged thymus glands, and other ailments. X-rays were also used to measure foot sizes in shoe stores, and many people fondly remember seeing their “glowing green feet” and playing in these shoe fluoroscopes for hours while siblings were fitted for shoes. Children, younger than 15 years old, are most sensitive to radioactive damage to their thyroids.

Medical Therapy
Radiation therapy to the head, neck, and upper chest are an increasingly common cause of radiation induced thyroid cancer. Lymphoma, head and neck cancers, lung cancer, and breast cancer are some of the more common cancers that are associated with radiation exposure to the thyroid.

Environmental exposure
Thyroid cancer can be caused by radioactivity released from nuclear incidents such as the 1986 nuclear accident at the Chernobyl power plant in Russia. Many of the children in areas of Russia and the Eastern Block countries were inadvertently exposed to radiation and went on to develop thyroid cancer. Some people may also be exposed to radiation at work. However, routine X-ray exposure (for example dental X-rays, chest X-rays, mammograms) have NOT been shown to cause thyroid cancer.

Genetics
Papillary thyroid cancer can run in the family and may be associated with genetic syndromes. Although rare, PTC can also be associated with goiters or colonic tumors. Therefore, patients should ask their relatives for a family history of papillary thyroid cancer, goiter, colon/rectal tumors, or breast cancer. Patients with a positive family history are more at risk for thyroid cancer than those with no family history.

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The American Association of Endocrine Surgeons (AAES)

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