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Medullary vs Papillary Thyroid Cancer

Thyroid cancer occurs when abnormal cells grow uncontrollably in the thyroid gland, forming a tumor. While all thyroid cancers originate in the same organ, key differences exist between the two most common types – medullary and papillary. Understanding their unique risk factors, genetics, symptoms, outlooks, and tailored therapies empowers patients to confront the disease.

Key Differences Between Medullary and Papillary Thyroid Cancers

Medullary thyroid cancer accounts for about 4% of all thyroid cancer cases, while papillary thyroid cancer makes up around 80%. Here are some of the main differences between the two:

  • Origins: Medullary thyroid cancer starts in the C cells of the thyroid which produce calcitonin hormone. Papillary cancer begins in follicular cells of the thyroid that are responsible for making thyroid hormones.
  • Gender predilection: Medullary cancer affects men and women equally. Papillary cancer is 3 times more common in women.
  • Genetics: Medullary cancer can be inherited. Most papillary cancers occur sporadically.
  • Spread: Medullary cancer can spread to lymph nodes, lungs, liver, and bones. Papillary cancer typically metastasizes to nearby lymph nodes first.
  • Prognosis: Medullary cancer has a less favorable outlook compared to papillary thyroid cancer.

Recognizing the Symptoms

In the early stages, both medullary and papillary thyroid cancers may not cause any noticeable symptoms. As the tumors grow larger, some common signs can include:

  • A visible lump or nodule in the front of the neck
  • Swollen lymph nodes in the neck
  • Hoarse or changing voice
  • Difficulty breathing or swallowing
  • Chronic cough (not due to cold)

Medullary cancer can sometimes cause diarrhea or flushing episodes. Symptoms depend on the extent of tumor spread. Many cases are diagnosed incidentally during imaging tests for other neck or chest issues.

How Medullary and Papillary Thyroid Cancers Are Diagnosed

If a thyroid nodule is detected during a physical exam or imaging study, doctors will investigate further to determine if it is cancerous. Typical diagnostic steps include:

  • Blood tests – to check levels of thyroid hormones and tumor markers like calcitonin
  • Imaging – ultrasound, CT scan, MRI, or PET scan to visualize the thyroid and surrounding region
  • Biopsy – fine needle aspiration or surgical biopsy to extract cells for examination under a microscope
  • Genetic testing – for medullary thyroid cancer to look for RET gene mutations

These tests help confirm the diagnosis and determine the cancer type – medullary or papillary. Staging exams are then done to assess the spread of the disease.

Risk Factors and Causes

Certain factors can raise one’s risk of developing thyroid cancer:

Medullary Thyroid Cancer

  • Family history – 25% of cases are inherited due to RET gene mutations
  • Multiple endocrine neoplasias – a rare hereditary syndrome
  • Radiation exposure – controversial and not a proven cause

Papillary Thyroid Cancer

  • Radiation exposure – especially in childhood
  • Family history – 5-10% of cases are inherited
  • Unhealthy weight – obesity increases risk in women
  • A diet low in iodine – can cause thyroid dysfunction
  • Breast cancer – papillary thyroid cancer risk is higher in survivors

Though both cancers affect the thyroid, their causes, and risk factors differ considerably.

Treatment Approaches for Each Type

Treatment plans are tailored based on the type of thyroid cancer, its stage, and the patient’s overall health profile.

Medullary Thyroid Cancer Treatment

As medullary thyroid cancer can spread aggressively, the primary treatment is the surgical removal of the thyroid gland and surrounding lymph nodes. Additional therapies include:

  • Targeted drug therapy – using tyrosine kinase inhibitors like vandetanib and cabozantinib
  • Immunotherapy – to stimulate the immune system against cancer cells
  • Radiation therapy – for pain relief and reducing tumor size
  • Chemotherapy – can be combined with radiation in advanced stages

Papillary Thyroid Cancer Treatment

Most papillary thyroid cancers have an excellent prognosis with treatment. Usual therapies include:

  • Radioactive iodine therapy – to destroy any remaining thyroid tissue after surgery
  • Thyroid hormone therapy – to replace hormones no longer made by removed thyroid
  • Targeted therapy – rarely needed for advanced papillary thyroid cancers

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Prognosis and Outlook

Thyroid cancer survival rates can vary substantially based on the type, stage at diagnosis, and effectiveness of treatment.

Medullary Thyroid Cancer Prognosis

If detected early when still localized, the 5-year survival rate for medullary thyroid cancer is over 99.5%. However, the rate drops to 92% for regional disease and 43% for metastatic cancer. Periodic monitoring and early intervention for recurrence are critical.

Papillary Thyroid Cancer Prognosis

Papillary thyroid cancer has an excellent prognosis overall. The 5-year relative survival rate is over 99.5% for localized tumors and 99% for regional stage disease. Even if spread to distant lymph nodes and organs occurs, 5-year survival remains high at 74%.

Younger age, small tumor size, and minimal spread indicate more favorable outcomes for both cancer types.

Likelihood of Recurrence

Cancer recurrence means the disease has come back after treatment. Monitoring for possible recurrence is a lifelong process for thyroid cancer survivors.

For medullary thyroid cancer, the recurrence risk is estimated to be up to 50% even with successful surgery. Recurrence usually happens within the first 2-3 years after initial treatment.

Recurrence rates for papillary cancer range from 8-28% depending on initial tumor characteristics like size, spread to lymph nodes, and cancer genetics. Periodic long-term follow-up exams are recommended to detect any recurrence or new tumors early when they are most treatable.

Genetics Behind Thyroid Tumors

Genes influence risk for both medullary and papillary thyroid cancers.

Around 25% of medullary thyroid cancer cases are inherited through autosomal dominant transmission of the RET gene mutation from a parent. Sporadic mutations also occur.

For papillary thyroid cancer, the BRAF gene mutation and RET/PTC rearrangements are the most common genetic changes identified in tumor cells. Overall, genetics contribute to 5-10% of cases.

Medical Terms to Know

  • Adenocarcinoma: A type of cancer that starts in cells that line organs and glands.
  • C cells: Cells in the thyroid gland that produce calcitonin.
  • Follicular cells: Cells in the thyroid gland that make thyroid hormones.
  • Genetics: The study of genes and how they influence inherited traits.
  • Hormones: Chemicals that are produced by glands in the body and travel through the bloodstream to organs and tissues, where they have specific effects.
  • Iodine: A mineral that is essential for the production of thyroid hormones.
  • Metastasis: The spread of cancer cells from one part of the body to another.
  • Papillary thyroid cancer: A type of thyroid cancer that starts in the follicular cells.
  • Prognosis: The outlook for a disease based on its expected course and outcome.
  • Thyroid gland: A small gland in the neck that produces hormones that help regulate metabolism, growth, and development.
  • Thyroid hormone: A hormone that is produced by the thyroid gland and helps regulate metabolism, growth, and development.

Key Takeaways

Though both are thyroid cancers, medullary and papillary types start from different cell origins and have varying risk factors, behavior, and prognoses.

Papillary cancer is far more common and typically has better outcomes, while medullary cancer can be more aggressive, spreading to distant organs.

Treatment options include radioiodine therapy, thyroid ablation, or radiation may be used as needed for tumors.

Resources

Medullary Thyroid Cancer – NCI

Papillary Thyroid Cancer | Columbia Surgery

Sex Differences in Papillary Thyroid Cancer – ScienceDirect

Medullary Thyroid Cancer Genetics

Papillary Thyroid Cancer Affecting Multiple Family Members: A Case Report and Literature Review of Familial Nonmedullary Thyroid Cancer

Thyroid Cancer Survival Rates, by Type and Stage

Update on the Diagnosis and Management of Medullary Thyroid Cancer: What Has Changed in Recent Years? – PMC

Evaluation of recurrence risk in patients with papillary thyroid cancer through tumor-node-metastasis staging: A single-center observational study in Taiwan – ScienceDirect

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