From suspicion to diagnosis, how do doctors figure out the true nature of thyroid cancer step by step? What are the “weapons” that need to be used? The first step in the process is to identify the presence of thyroid cancer. This article will give you a glimpse.
The doctor’s diagnosis begins with a detailed history and a “hands-on” examination, but these are not enough. The next step is usually laboratory tests to initially suggest thyroid function, imaging to initially determine benignity, and pathology to “seal the deal.
The clinical diagnosis of thyroid cancer is based on clinical symptoms, signs, laboratory tests, imaging, and pathology.
Symptoms
Thyroid cancer, depending on its location and size, can produce symptoms such as neck pain, difficulty breathing, difficulty swallowing, and hoarseness. If thyroid hormone levels are affected, patients may also have symptoms of hyperthyroidism (panic attacks, fever and palpitations, excessive sweating and weight loss, protruding eyes, etc.) or hypothyroidism (loss of appetite, mental decline, unresponsiveness, drowsiness, edema, etc.).
However, thyroid cancer can be asymptomatic. In fact, the vast majority of patients with thyroid cancer are currently clinically asymptomatic.
Signs
Signs are physical signs of thyroid cancer that are mainly obtained by physical examination by a physician.
When palpating the neck, the physician will look for centered trachea, enlarged thyroid, nodules in the thyroid, size and texture of the nodules, adhesions to surrounding muscles, extension behind the sternum, and palpable enlarged lymph nodes in the lateral neck, texture and size of the lymph nodes. The presence of these signs can directly influence the surgical approach.
Laboratory tests
Laboratory tests unique to the thyroid gland are primarily thyroid function measurements. They usually cover thyroid hormones (T3, T4, FT3, FT4), thyrotropin (TSH), thyroglobulin TG, thyroglobulin antibody TGAb, thyroid autoimmune antibody TPOAb, calcitonin CT, parathyroid hormone PTH, and carcinoembryonic antigen CEA to assess whether the patient has abnormal thyroid function (eg. PTH can be used to determine parathyroid function, whereas CT and CEA are suggestive of medullary thyroid cancer).
The purpose of laboratory tests is to 1) clarify whether there is a contraindication to surgery, such as hyperthyroidism; 2) to indicate whether the mass in the thyroid gland is of parathyroid origin; and 3) to indicate whether the thyroid nodule is a medullary thyroid carcinoma.
In addition to thyroid function, preoperative blood tests such as routine blood, liver and kidney function, and blood clotting are required to screen patients for contraindications to surgery.
Imaging
Currently, commonly used imaging tests of the thyroid are neck ultrasound and neck-enhanced CT.
Ultrasound is the preferred test for thyroid nodules, providing initial clarification of the presence or absence of occupancy in the thyroid, helping the physician determine the benignity or malignancy of the thyroid nodule based on what is within the occupancy, and giving an ultrasound TI-RADS grade. The judgment of ultrasound findings is somewhat subjective. Therefore, patients may get inconsistent grading results from ultrasound exams done at different hospitals. Ultrasound can also detect cancerous clots in the cervical lymph nodes and blood vessels and make a preliminary determination of the benignity or malignancy of the lymph nodes. Because the interpretation of ultrasound images is subjective to the physician, ultrasound is not a strong preoperative guide for the thyroid.
Enhanced CT of the neck is complementary to ultrasound. CT can detect ectopic thyroid or retrosternal thyroid, and it can also provide a predictive judgment of the malignancy of the nodule by its internal density. The greatest value of CT is in determining the adjacency of thyroid nodules and cervical lymph nodes to surrounding organs and blood vessels, providing the surgeon with a wealth of information to develop a rational surgical plan.
Other imaging studies, such as MRI and PET-CT, are not necessary in thyroid cancer. MRI may be used when there is an allergy to iodine or when the nodule needs to be evaluated in relation to soft tissue, and PET-CT is indicated for patients with suspected systemic metastases.
Pathologic examination
Preoperative pathology is performed to clarify the nature of the thyroid nodule or cervical lymph node. Fine needle aspiration is the most sensitive test to determine thyroid nodules preoperatively.
Preoperative puncture can also be performed in conjunction with genetic testing, which is commonly used clinically for the BRAF and TERT genes. The presence of mutations in these genes suggests that the patient is at a higher risk of recurrence. If the puncture results are inconclusive, a positive ancillary genetic test may also predispose the clinician to surgical resection.
Fine needle aspiration of the cervical lymph nodes can also be combined with eluate TG testing to help determine if the cancer cells in the lymph nodes are of thyroid origin.
Other tests
Preoperative laryngoscopy is also an option for patients who are at risk for intraoperative laryngeal nerve injury or who have preoperative voice changes, which can clarify laryngeal nerve injury and provide guidance to the surgeon.
Co-written by Dr. Jiaqian Hu, Cancer Hospital of Fudan University