Papillary Thyroid Cancer

Papillary thyroid cancer is the most common form of thyroid cancer, accounting for about 80 to 85 percent of all cases. While hearing a cancer diagnosis can be frightening, this type of thyroid cancer typically grows very slowly and has an excellent prognosis, with most patients achieving successful treatment outcomes.

Table of contents

• What is papillary thyroid cancer?
• Who does it affect?
• Associated anatomy
• Subtypes of papillary thyroid cancer
• Signs and symptoms
• Causes and risk factors
• How the cancer spreads
• Diagnosis
• Treatment options
• Prognosis and survival
• Follow-up care

What is papillary thyroid cancer?

Papillary thyroid cancer begins in the follicular cells in your thyroid that produce a protein called thyroglobulin. It is the most common type of thyroid cancer^[1]. The cancer is also called papillary thyroid carcinoma, where carcinoma is a medical term meaning a cancer that starts in cells that line the inside or outside surfaces of the body^[1].

Papillary thyroid cancer tends to grow very slowly and usually develops in only one lobe of your thyroid gland^[1]. The tumor usually appears as an irregular solid mass, but it may have cystic features in rare cases^[3].

Papillary thyroid cancer is fairly common, accounting for 80 to 85 percent of all thyroid cancer cases^[1]. It is one of the fastest growing cancer types with over 20,000 new cases a year in the United States^[2].

Who does it affect?

Papillary thyroid cancer can affect anyone, but it most commonly occurs in middle-aged adults, with peak onset ages between 30 and 50 years^[1][7]. Women are more likely to develop papillary thyroid cancer than men, with a ratio of about 3 to 1^[7]. In fact, it is the 8th most common cancer among women overall and the most common cancer in women younger than 25^[2].

Although papillary thyroid cancer is rare in children, it is still the most common pediatric thyroid cancer^[1].

Associated anatomy

• Thyroid gland
• Neck lymph nodes

Your thyroid is a small, butterfly-shaped gland located at the front of your neck under your skin, at the base of the throat near the windpipe. It is part of your endocrine system, a network of glands that produce hormones to control many of your body’s important functions^[1]. The thyroid produces hormones that control heart rate, body temperature, metabolism, and help keep the brain, heart, muscles, and other organs working properly^[4].

Subtypes of papillary thyroid cancer

There are several subtypes of papillary thyroid cancers. The follicular subtype, also called mixed papillary-follicular variant, is the most common^[1]. Other subtypes of papillary cancer are not as common and tend to grow and spread more quickly. These include columnar, tall cell, insular, and diffuse sclerosis subtypes^[1].

Signs and symptoms

Most papillary thyroid cancers do not cause symptoms. In fact, many patients will not know that they are there^[2]. The main sign of papillary thyroid cancer is a painless lump or nodule on your thyroid gland. Papillary thyroid cancer usually does not cause any other symptoms^[1].

Patients with large nodules may notice a mass they can feel or see. Very large nodules may cause compressive symptoms, which include difficulty swallowing, food or pills getting stuck when they swallow, and pressure or shortness of breath when lying flat^[2].

In rare cases, you may experience pain in your neck, jaw or ear from papillary thyroid cancer. If the nodule is large enough to compress your windpipe or esophagus, it may cause difficulty with breathing or swallowing^[1]. In cases of advanced cancer that are growing into surrounding structures, patients may develop hoarseness or difficulty swallowing^[2].

Enlarged neck lymph nodes that are concerning for cancer include those that are non-tender, firm, growing, and do not shrink over time. Patients with compressive symptoms, enlarged lymph nodes, hoarseness, or a rapidly growing nodule should seek medical evaluation right away^[2].

Causes and risk factors

Scientists still do not know the exact cause of papillary thyroid cancer, but they have identified risk factors that increase your risk of developing this disease^[1]. It is important to note that the majority of patients have no risk factors at all^[2].

The rates of papillary thyroid cancer are higher in people who have a history of exposure to significant ionizing radiation, which is a type of high-energy radiation^[1]. This exposure could be due to high-dose external radiation treatments to your neck, especially during childhood, used to treat cancer or some noncancerous conditions. External low-dose radiation therapy to the head and neck during childhood, used in the 1940s to 1960s to treat various benign diseases, predisposes to papillary thyroid cancer. The average time from radiation exposure to tumor recognition is approximately 10 years but may be longer than 30 years^[3].

Radiation exposure from nuclear plant disasters can also increase risk. The Chernobyl nuclear accident in 1986 led to a 3- to 75-fold increase in papillary thyroid cancer cases in fallout regions, especially in younger children^[1][3].

A few genetic conditions are associated with papillary thyroid cancer, including familial adenomatous polyposis (also called Gardner syndrome), Werner syndrome, and Carney complex type 1^[1][3]. Familial papillary thyroid cancer cases have been reported in 5 percent of all patients with papillary thyroid cancer and may portend a more aggressive disease course^[3].

Papillary thyroid cancer is higher in regions with high dietary iodine intake and in patients with preexisting benign thyroid disease^[3]. There is also a trend for an increased incidence of thyroid cancer due to being overweight or obese^[3].

How the cancer spreads

Even though papillary thyroid cancer grows slowly, it often spreads to the lymph nodes in your neck. Lymph nodes are small bean-shaped structures that are part of your body’s lymphatic system and immune system^[1]. About 30 percent of people have metastatic papillary thyroid cancer, meaning cancer that has spread to other parts of their body, at the time of diagnosis^[1].

Up to 20 percent of patients will have involved lymph nodes at the time of diagnosis. However, unlike other cancers where involved lymph nodes means a very poor prognosis, in thyroid cancer involved lymph nodes usually have almost no impact on survival. Involved lymph nodes may increase the chance of recurrence, meaning the cancer coming back, but they do not change the prognosis^[2].

One key feature of papillary thyroid cancer is its ability to invade adjacent structures like lymphatics. About 10 percent of patients may present with metastatic disease at initial presentation^[3].

Diagnosis

When a thyroid nodule is discovered, a complete history and physical examination should be performed. In particular, the doctor is looking for risk factors for cancer that include a family history of thyroid cancer, a history of radiation exposure to the head, neck, or chest, age less than 20, age greater than 70, male gender, very hard nodules, enlarged lymph nodes, or hoarseness^[2].

After the history and physical exam, a TSH level (thyroid stimulating hormone) should be checked to see if the patient has normal thyroid function, an overactive thyroid, or an underactive thyroid. In general, it is unusual for patients with overactive thyroid to have cancer, while patients who have underactive thyroid may have a slightly higher rate of cancer. Most patients with thyroid cancer have normal thyroid function^[2].

The next step in the work-up is an ultrasound of the neck. There is no radiation associated with an ultrasound. An ultrasound is the best test to look at the thyroid and will allow the doctor to see the size of the thyroid and specific features of the nodule^[2].

If a nodule appears concerning, a fine needle aspiration biopsy is performed. During this procedure, a thin needle is inserted into the nodule to collect a small tissue sample. The sample is then examined under a microscope by a specialist to determine if cancer cells are present^[2]. In some cases, a molecular analysis of the biopsy sample may also be done to help confirm the diagnosis and determine the best course of treatment^[2].

Additional tests, such as blood tests to check thyroid hormone levels, may also be part of the diagnostic process. Genetic testing may be done on the biopsy sample to see what genetic changes may be present. Knowing this may help guide treatment recommendations^[1].

Treatment options

Surgery is usually the main treatment for papillary thyroid cancer^[1]. The type of surgery done depends on your age, the size of the tumor, and if the cancer has spread outside the thyroid^[1].

Total thyroidectomy is removal of the entire thyroid gland. It is the most common type of surgery used for papillary thyroid cancer. It is done if the doctor plans to use radioactive iodine therapy after surgery^[13].

Lobectomy is removal of one part, or lobe, of the thyroid. It may be done for some low-risk cancers. Lobectomy may be used if the area has never been exposed to radiation, there are no distant metastases, the tumor is only in the thyroid, and the tumor is 1 to 4 centimeters in diameter^[13].

Neck dissection removes lymph nodes from the neck. The surgeon may also remove other tissues around the thyroid. It is done if a biopsy shows there is cancer in the lymph nodes in the neck or the doctor thinks there is cancer in these lymph nodes based on the results of imaging tests such as an ultrasound^[13].

After surgery, you may receive radioactive iodine therapy, which is often taken by mouth. This substance kills any remaining thyroid tissue. It also helps make medical images clearer, so doctors can see if there is any cancer left behind or if it comes back later^[1][6].

After surgery or radioactive iodine therapy, you will need to take medicine called levothyroxine for the rest of your life. This replaces the hormone the thyroid would normally make^[1][6].

For some very small, low-risk papillary thyroid cancers, active surveillance may be used. Active surveillance involves watching the cancer with regular tests and exams to check if it is starting to grow or cause symptoms^[13]. In active surveillance, patients have neck ultrasounds twice a year for two years to monitor changes, if any, in the tumor. In the past 10 to 20 years, more than 85 percent of patients who chose active surveillance never needed surgery because their tumors did not grow or spread to their lymph nodes^[23].

External radiation therapy may be used in rare cases if the cancer is larger, aggressive, or has spread to nearby tissues. This involves using high-energy rays to target and kill cancer cells^[1].

For recurrent papillary thyroid cancer, meaning the cancer has come back after it has been treated, treatment will depend on where the cancer recurs. If the cancer is in the neck, it may be removed with surgery if possible. Radiation therapy may also be used, either alone or with surgery. Targeted therapy or chemotherapy may be used if the cancer has spread to several places and does not respond to radiation therapy^[13].

Prognosis and survival

While all cancer types are serious in that they require medical treatment and have the potential to spread to other parts of your body, papillary thyroid cancer has the best overall prognosis of all thyroid cancer types. Papillary thyroid cancer can often be treated successfully and is rarely fatal^[1].

The survival rate for papillary thyroid cancer is excellent. More than 90 percent of adults with this cancer survive at least 10 to 20 years^[6]. The five-year survival rate for papillary thyroid cancer that has not spread outside of the thyroid gland is almost 100 percent. The five-year survival rate for papillary thyroid cancer that has only spread to lymph nodes or tissue in the neck is 99 percent. If there is distant spread to other parts of the body outside of the neck, the five-year survival rate is 76 percent, which is excellent compared to many other types of cancer^[20].

The overall cure rate for papillary thyroid cancer approaches 95 percent. Most patients with papillary thyroid cancer will not die of this disease^[2][20].

The prognosis is better for people who are younger than 40 and for those with smaller tumors. The following factors may decrease the survival rate: being older than 55 years of age, cancer that has spread to distant parts of the body, cancer that has spread to soft tissue around the thyroid, and large tumors^[6].

The prognosis is generally determined by several factors, including the patient’s age, the size of the tumor, and whether the cancer has spread to lymph nodes or other parts of the body. Cancers that are confined to the thyroid gland have the most favorable prognosis^[2].

Follow-up care

Even after treatment, regular follow-up appointments are important to monitor for any recurrence of cancer. Your doctor will likely recommend blood tests, including thyroglobulin levels, and neck ultrasounds to track your progress and detect any signs of cancer returning^[11].

Your provider will likely have you take a blood test every several months to check thyroid hormone levels. Other follow-up tests that may be done after treatment for thyroid cancer include ultrasound of the thyroid, an imaging test called a radioactive iodine uptake scan, and repeat fine needle aspiration biopsy^[6].

Your quality of life is very unlikely to be negatively affected by thyroid cancer surgery done correctly in the hands of experts. You may have to take thyroid hormone medication after thyroid removal. As long as you are compliant with the necessary medication and follow-up, then your thyroid levels should be appropriate. If your thyroid levels are where they should be, then thyroid medication or thyroid cancer surgery will not be the cause of weight gain, fatigue, hair loss, or other concerns. The reality is, almost everyone on thyroid hormone medication will do great as long as they take the medication as directed, get their thyroid levels checked 1 to 2 times yearly at a minimum, and maintain a healthy lifestyle^[20].

papillary thyroid carcinoma, PTC