Work-up

The most common place for WDTC’s to spread is via the lymphatic system to the lymph nodes in the neck.

• WDTC’s generally spread very predictably like passengers riding on a train from stop to stop – rarely do they ever skip stops.
  • First to the lymph nodes in the central neck (between the trachea and carotid artery), then the lymph nodes in the lateral neck (to the outside, or on the other side of the carotid artery), then very rarely to the lungs, then elsewhere distantly in the body.
    • WDTC very rarely cross midline due to the way the lymphatic system develops (i.e. left sided thyroid cancers will not spread to lymph nodes in the right side of the neck, and vice versa).
      • WDTC located in the isthmus (central part of the thyroid), may have the potential to spread either the right and/or left side of the neck.
• The best way to assess for cancer spreading to the lymph nodes in the neck is looking with a detailed ultrasound of the neck (aka ‘lymph node mapping’), +/- a CT Scan of the Neck with contrast.
  • At least one of these imaging studies should be performed once the diagnosis of thyroid cancer is made.
    • Consider CT scan of the Neck with contrast for large cancers, suspected invasion to local structures, cancer that has proven to spread to a lymph node by FNA (biopsy), and aggressive WDTC subtypes diagnosed on FNA.
      • CT can sometimes detect lymph nodes in areas where ultrasounds cannot (behind the esophagus or pharynx, in the upper chest / mediastinum, behind the carotid artery / internal jugular vein).
    • Iodine from the contrast of a CT scan will not affect the ability to receive radioactive iodine treatment following surgery if needed.
      • Iodine from the contrast of a CT scan “is generally cleared within 4 – 8 weeks in most patients, so concern about iodine burden from IV contrast causing a clinically significant delay in subsequent whole-body scans or radioactive iodine (RAI) treatment after surgery is generally unfounded. The benefit gained from improved anatomic imaging generally outweighs any potential risk of a several week delay in RAI imaging or therapy.”
        • 2015 ATA Management Guidelines for Adults with Differentiated Thyroid Cancer.
  • Since it is incredibly rare for WDTC to spread beyond the neck, imaging of the Chest (lungs) and the rest of the body is not indicated unless there is suspicion for very aggressive disease at the time of diagnosis, or suggestion of distant spread of the cancer following surgery (i.e. very highly elevated thyroglobulin levels).
    • Measuring thyroglobulin levels (tumor marker for WDTC’s) prior to surgery is not indicated because it is not an accurate reflection of how much cancer is in the body when the entire thyroid is still present.
    • For intermediate to high risk WDTC’s that do receive radioactive iodine (RAI) following surgery, a whole-body scan is performed one week after taking the iodine pill which can assess for spread outside the neck.
    • PET scans are not sensitive in detecting most WDTC’s and are not indicated for the initial work-up or routine surveillance.
• If a suspicious lymph node is identified on imaging prior to surgery, it should be biopsied (FNA’d).
  • If not feasible based on location, size, or other reasons, an excisional biopsy with frozen pathologic interpretation (aka frozen biopsy) during the surgery can be performed.
• Sometimes, despite best efforts to identify atypical lymph nodes prior to surgery, an atypical lymph node may only be appreciated during surgery.
  • This lymph node can be removed and sent for a frozen biopsy during surgery.
  • If + for spread of cancer, the surgeon will act accordingly to perform the indicated surgery to give you the best chance of a cure.
    • Total thyroidectomy with central neck dissection.

Invasion can sometimes be seen on ultrasound but not always.

If there is concern for invasion based on symptoms (shortness of breath, change in voice, difficulty swallowing, etc.), physical exam (large tumor, fixed, large lymph nodes), or ultrasound findings there should be a low threshold to obtain a CT scan of the neck with contrast (better at assessing the presence and extent of invasion).

• If invasion is noted or highly suspected, this will affect the decision on extent of surgery needed and pre-operative counseling.
  • Total thyroidectomy with central neck dissection is recommended when invasion is present.
  • More aggressive surgery such as tracheal resection (removing portion of the trachea where the cancer is invading) may also be needed.
    • Better for the surgeon and patient to be prepared for this prior to surgery.

Sometimes, despite best efforts to identify invasion to nearby structures prior to surgery, this may only be appreciated by the surgeon during surgery.

• If this is appreciated during surgery, the surgeon will act accordingly to perform the indicated surgery to give you the best chance of a cure.
  • Total thyroidectomy with central neck dissection.

Prior to surgery, an examination of the vocal cords should be performed to ensure the nerves controlling the movement of the vocal cords (recurrent laryngeal nerve) do not have pre-existing dysfunction or have been compromised by the presence of the cancer (invading or surrounding the nerve).

• Typically performed in the office with a flexible laryngoscopy camera.
  • Camera is roughly the size and shape of a large spaghetti noodle.
  • Travels through the nose to get a view from above the voice box (larynx) and vocal cords.
  • Takes 2 min or less, usually easier than a COVID nasal swab.
• If there is suspicion that the cancer is affecting the nerve based on symptoms, imaging, and/or laryngoscopy exam, there is an increased likelihood that the nerve will need to be sacrificed (cut in order to remove all the cancer) during the surgery.