Do I have to have a full body checkup?
When thyroid cancer is diagnosed, your doctor will assess the risk of metastasis and decide if a thorough whole-body exam is needed to clarify metastasis.
Usually, thyroid cancer progresses slowly, with the most common site of metastasis being the cervical lymph nodes and, more distantly, the mediastinal lymph nodes; true distant metastasis is less common. Once it occurs, the most common sites are lung and bone, with occasional metastases to organs such as the brain and adrenal glands.
Thus, cervical lymph nodes are routinely the ones that need to be carefully screened. If the physician determines that the risk of distant metastases is low, there is no need for a whole-body examination, and most patients in the clinic fall into this category. However, some patients with a high risk of metastasis may be recommended by their physicians for a whole-body workup, which is important for choosing a surgical and combination treatment option.
When is a whole-body workup needed?
The risk of metastasis is high when you have the following conditions:
- Higher malignancy of pathological type, such as hypodifferentiated or undifferentiated carcinoma, medullary carcinoma, etc.; specific pathological types, such as squamous carcinoma, lymphoma, etc.
- Severe metastasis from primary foci and cervical lymph nodes
- Symptoms of metastatic foci, such as bone pain
What tests may be needed?
There are three main types of tests commonly used to look for distant metastases: imaging, pathology, and tumor marker tests.
Imaging:
- B ultrasound: examining the neck, body surface, and abdominal organs
Related reading:
- CT: look for lung and bone metastases, may be useful
Thoracic enhancement CT exams can be used to detect lung metastases. If multiple or diffuse cornular or nodular lesions of varying size, mostly round or round-like, are found in both lungs, and after other lung disease or metastases from other tumors have been ruled out, your doctor may consider lung metastases from thyroid cancer.
CT exams of suspicious sites can also evaluate bone metastases.
It is sensitive, but can be “false positive” (suggesting a lesion that is not actually a metastasis), so even if the result is positive, CT or MRI is still needed to make a definitive diagnosis.
- Nuclear imaging: good for tracking differentiated thyroid cancer, residual, recurrent and metastatic lesions after total thyroidectomy
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Radioiodine 131 (I-131) imaging is most commonly used.
Differentiated thyroid cancers (papillary and follicular carcinomas) can ingest iodine, and whole-body imaging with radioiodine allows tracking of residual, recurrent, and metastatic lesions after surgery.
However, normal thyroid tissue also has iodine uptake, so this test is only indicated for patients after total thyroidectomy to avoid interference.
In addition, some thyroid cancers can mutate and lose their iodine uptake, so metastases cannot be completely ruled out, even if the imaging result is negative.
Related reading:
- PET-CT: suitable for comprehensive detection of systemic metastases
Particularly for more malignant thyroid cancers, it can be used for preoperative assessment of systemic metastases and to help physicians develop comprehensive treatment plans.
In addition, PET-CT can also be used for post-treatment evaluation and monitoring of thyroid cancer, especially in cancers that do not ingest iodine.
Pathology
Metastases that are suspected clinically and on imaging can be diagnosed by puncture or other means to obtain tissue for pathology.
For example, in a suspected pulmonary nodule, the physician can obtain CT-guided puncture tissue from the nodule and, based on the pathology, can clarify the nature of the nodule to guide treatment.
Tumor markers
In patients with differentiated carcinoma who have had total thyroidectomy, dynamic testing of serum Tg (thyroglobulin) levels can help assess tumor recurrence. Once Tg is dynamically elevated, it suggests the possibility of metastasis or recurrence.
Related reading
Patients with medullary thyroid carcinoma, if postoperative serum CT (calcitonin) levels are dynamically elevated, it also suggests that the tumor may have metastasized and recurred.
Please understand that your doctor cannot diagnose metastatic or recurrent thyroid cancer based on these elevated blood levels alone. The definitive diagnosis still depends on imaging and pathology.
Summary
Overall, thyroid cancer is unlikely to metastasize distantly, and most patients do not require a systemic workup. Patients whose physicians assess a high risk of metastasis, or whose clinical symptoms suggest the possibility of distant metastasis, may have imaging; patients with differentiated carcinoma and post-total thyroidectomy may be evaluated for tumor residual and metastasis throughout the body by nuclear imaging. Tumor markers can also be referred. Ultimately, pathological examination is needed to confirm the diagnosis.
Co-written by Dr. Yiming Cao, Cancer Hospital of Fudan University