Medullary thyroid cancer is a rare form of thyroid cancer, accounting for 5 percent of thyroid cancer diagnoses. Detecting the cancer early can be difficult.

Medullary thyroid cancer commonly advances from the thyroid into the lymph nodes. Undiagnosed medullary thyroid cancer can spread into other neck tissues and eventually reach the liver, lungs, bone, and brain. Once it reaches distant parts of the body it’s unlikely to be cured.

The earlier medullary thyroid cancer is found, the more likely it can be stopped and treated. Unfortunately, there may be no early warning signs of this type of cancer.

The noticeable signs and symptoms like hoarseness, difficulty swallowing, or throat lumps often don’t appear until the tumor has advanced.

While not everyone will have the same symptoms, here are some of the most common signs of medullary thyroid cancer:

  • Neck lump. A single lump on the front of the neck is the most common symptom. It’s often discovered during a routine physical exam. Lumps in the thyroid area and neck are usually benign, but if you notice unusual swelling in your neck, contact your doctor immediately.
  • Neck pain. Pain in the front of the neck may be related to the growth of a thyroid tumor. This pain can also extend to the ears.
  • Hoarseness. The nerve that controls your vocal cords runs alongside the trachea near the thyroid. If cancer has spread to that vocal cord, it can affect the quality of your voice.
  • Coughing. Thyroid cancer can sometimes cause a persistent cough. You should see your doctor if you have a cough that’s unrelated to a cold or one that doesn’t go away.
  • Trouble swallowing (dysphagia). If a thyroid tumor becomes large enough, it can press on the esophagus and make swallowing difficult.
  • Shortness of breath (dyspnea). Similar to trouble swallowing, if a thyroid tumor is large enough, it can push against the windpipe and interfere with breathing.

Other, more rare or unusual signs of medullary thyroid cancer that you should be aware of include:

  • Severe diarrhea. This is a very rare symptom sometimes found in people with advanced medullary thyroid cancer. The tumor produces high levels of calcitonin, a hormone that may cause severe diarrhea.
  • Cushing syndrome. In rare cases, adrenal tumors can cause Cushing syndrome, a condition that arises when a tumor secretes hormones that the thyroid wouldn’t normal create. Cushing syndrome associated with medullary thyroid cancer is uncommon. The syndrome is more commonly caused by the pituitary gland overproducing adrenocorticotropic hormone (ACTH), or by taking oral corticosteroid medication.
  • Facial flushing. A red face, neck, or chest paired with warm or burning sensations can be a sign of many conditions. Tumors or other abnormal growths can overproduce hormones, triggering flushing. The symptom can also be a response to certain drugs, foods, alcohol, or menopause.
  • Bone pain. People with medullary thyroid cancer may have bone pain if the cancer has spread to form bone lesions.
  • Lethargy. Many people with advanced cancer may feel physically, emotionally, or mentally tired. The causes of fatigue during cancer are complex and not well understood.
  • Weight loss. Unusual weight loss is a symptom of advanced medullary thyroid cancer that has spread beyond the thyroid into other organs.

If you experience any of these symptoms, especially if there’s a family history of medullary thyroid cancer, go see your doctor. Being attentive to your health is often one of the best ways to detect cancer early.