Thyroid cancer can become metastatic when cancer cells originating in the thyroid gland spread to other parts of the body through the bloodstream or lymphatic system (tissue, vessels, and organs carrying white blood cells back to the bloodstream). Only 3% of cases are metastatic at the time of diagnosis.

Once thyroid cancer metastasizes, it can affect various organs and tissues. Early detection of thyroid cancer is important to start treatment and improve outcomes. Thyroidectomy(removal of the thyroid gland) and other treatments may be performed to prevent metastasis and potentially cure thyroid cancer.

Most thyroid cancer cases (64%) are diagnosed while the cancer is localized in the thyroid, and 30% when it has spread only to regional lymph nodes but not to distant sites.

This article will review the most common sites of metastasis, the symptoms associated with metastatic disease, the types of thyroid cancer, and their progression.

~ Where in the Body Thyroid Cancer Spreads ~

The most common sites of thyroid cancer metastasis are:

* Lymph nodes in the neck

* Lungs

* Bones

* Liver

* Brain

* Adrenal glands

The lymph nodes in the neck are the most common sites of early metastasis due to the direct drainage of the thyroid gland into these nodes through the lymphatic system.

As the cancer progresses, it then spreads to distant sites via the bloodstream. The exact pattern of where thyroid cancer metastasizes can vary depending on the specific type of thyroid cancer and the characteristics of the tumor.

~ Stages of Thyroid Cancer ~

Thyroid cancer is assigned a stage from 1 to 4 at diagnosis. Consideration is given to the type of cancer and age at diagnosis and based on the following:

* Tumor size

* Involvement of nearby lymph nodes

* Whether the cancer has metastasized

~ Invisible Symptoms of Metastatic Thyroid Cancer ~

In the early stages of thyroid cancer, it is common to not have many noticeable signs or that the symptoms that are experienced are overlooked or attributed to something else. These initial signs and symptoms may include:

* Lump in the neck

* Voice changes

* Difficulty swallowing

* Neck pain

* Swollen lymph nodes in the neck

Metastatic thyroid cancer can also present with non-specific or invisible symptoms, which can make the diagnosis challenging. A person may experience symptoms that are attributed to other conditions. Symptoms can include:

* Cough

* Fatigue

* Unexplained weight loss

* Difficulty swallowing

* Hoarse voice

As the cancer progresses and involves various organs, other symptoms may appear, including:

* Shortness of breath

* Bone pain

* Abdominal discomfort

These subtle symptoms of metastatic thyroid cancer show the importance of regular monitoring and visits with a healthcare provider to detect metastasis early in those who have previously been treated for thyroid cancer.

~ Types of Thyroid Cancer and Progression ~

Metastatic thyroid cancer is one of a few various types of thyroid cancer. Each has its own characteristics and patterns of progression. The most common types of metastatic thyroid cancer include:

* Papillary

* Follicular

* Medullary

* Anaplastic

The rate at which thyroid cancer spreads can vary significantly and depends on several factors, such as:

* The type and subtype of thyroid cancer

* Tumor size

* Presence of metastases at diagnosis

Generally, thyroid cancer tends to be slow-growing, particularly in the case of papillary and follicular carcinomas (malignant tumors), which are the most common types. In the early stages, it is highly treatable.

Papillary thyroid cancer is the most common type of thyroid cancer and usually progresses slowly. If it spreads, it often is found in the lymph nodes in the neck before traveling to distant organs.

Follicular thyroid cancer, the second most common type of thyroid cancer, tends to spread through the bloodstream to distant organs, such as the lungs or bones.

Medullary thyroid cancer is much less common than papillary or follicular types, occurring in 3% to 5% of all thyroid cancers. It is also more aggressive than those types. This type can metastasize to the lymph nodes, lungs, liver, or bones.

Anaplastic thyroid cancer, a rare form of thyroid cancer, is highly aggressive and rapidly metastasizes to nearby tissues and distant organs, often leading to a poor prognosis.

~ Metastatic Thyroid Cancer After Thyroidectomy ~

A common treatment for early stage thyroid cancer is the surgical removal of the thyroid in a procedure called a thyroidectomy. Often it is done in an attempt to cure thyroid cancer.

Even though the primary tumor may have been removed, cancer cells may have already spread to other parts of the body before the surgery, or may develop metastases later on.

After a thyroidectomy, the person usually follows a schedule of careful monitoring to detect any signs of metastasis. This may involve regular imaging studies such as ultrasound, computed tomography (CT), iodine-131 diagnostic scans, or positron-emission tomography (PET) to assess for the presence of cancer cells in nearby lymph nodes or distant organs.

Additionally, blood tests that measure thyroid hormone levels and tumor markers may be performed to monitor for disease progression. Treatment options for metastatic thyroid cancer after thyroidectomy depend on a variety of factors, including the size and location of metastases, overall health status, and characteristics of the tumor.

Treatment options may include:

* Radioactive iodine therapy: Thyroid cells take up iodine, so administering a large dose of radioactive iodine can kill remaining thyroid cells.

* Targeted therapy: Tyrosine kinase inhibitors such as Nexavar (sorafenib) and Lenvima (lenvatinib) target the pathways the cancer cells use to grow.

* Chemotherapy: Medications are given that damage or kill activity dividing cells, such as cancer cells.

* External beam radiation: High-energy rays or particles are used to kill cancer cells in a specific location.

Collaboration among surgeons, endocrinologists (specialists in hormonal conditions), oncologists (cancer specialists), and other healthcare providers is important in managing metastatic thyroid cancer after thyroidectomy.

~ Summary ~

Thyroid cancer, though not uncommon and often very treatable, can spread to other parts of the body, which is called metastatic thyroid cancer. It can sometimes go unnoticed because the symptoms can be subtle. Common areas it spreads to include the lymph nodes, lungs, bones, liver, brain, and adrenal glands.

Early signs may include a lump in the neck, voice changes, or difficulty swallowing. Symptoms like fatigue, weight loss, and bone pain may develop as it progresses.

There are different types of thyroid cancer, with some being slow-growing and others more aggressive. After surgery to remove the thyroid, regular check-ups are important to catch any spreading early.

Treatment options include radioactive iodine therapy, targeted therapy, chemotherapy and radiation. Teamwork and collaboration between healthcare providers is necessary for the best care.

Editor’s NOTE: We strongly urge our readers to click on the two links directly above this note – “chemotherapy” and “radiation”. It is for YOUR benefit to understand EXACTLY what these two “options” will do to you. ~ Editor

Written by Julie Scott, MSN, ANP-BC, AOCNP for VeryWell Health ~ February 26, 2024
(Medically reviewed by Kelly Wood, MD)