What are the possible results of a thyroid puncture biopsy?

What are the results of a fine-needle aspiration (FNA) biopsy? Can you tell if you have thyroid cancer? Can you tell what type it is? What is the next step?

After a puncture biopsy, there are several possible findings

(1) Not diagnostic

Because the puncture only takes a portion of the cells for smear examination, sometimes there are not enough cells, broken cells that are not visible, or too many blood components. When the examining physician is not satisfied with the quality of the smear, he or she writes “not diagnostic”.

This is not a case that should be blindly considered benign. The next step is usually assessed by a surgical specialist depending on the condition: follow-up, re-puncture, or direct surgery.

(2) Benign lesions

FNA is usually very good at distinguishing common benign thyroid tumors, such as thyroid adenomas, nodular goiter, and other benign nodules.

If the biopsy report is “benign,” you usually don’t need to rush to surgery, and you can follow up with the hospital regularly. Some larger tumors, or tumors that are poorly located, may compress the trachea or esophagus, or are located behind the sternum, may also be recommended for surgery.

(3) Atypical lesions/follicular lesions of unknown significance

This means that the pathologist is seeing “atypical cells” under the microscope. These cells are different from normal thyroid cells, but they are also different from cancer cells and therefore cannot be clearly distinguished from benign or malignant.

Overall, the risk of malignancy is only 5%-15% when this result is seen, and the probability is benign; if the puncture is repeated, only half of the patients will be diagnosed. Clinical judgment is also usually made in conjunction with ultrasound and palpation by the physician.

The result is usually treated as benign, i.e., regular follow-up and rechecking of FNA if necessary.

(4) Follicular tumor/suspicious follicular tumor

This finding is more specific and includes both benign tumors (follicular adenoma) and malignant tumors (follicular carcinoma). Only postoperative pathology can clarify this, and FNA does not distinguish between benign and malignant. When this occurs, the risk of malignancy is about 15% to 30%.

Although the vast majority of follicular tumors are benign, they are potentially malignant after all, requiring a surgical expert to make a judgment call for surgery or other management.

(5) Suspected malignancy

This finding suggests a 60% to 75% risk of tumor malignancy and requires the surgeon’s judgment in combination with the B-ultrasound report and clinical palpation of the hand.

Generally treated clinically as malignancy, it usually requires aggressive surgical treatment and relies on postoperative pathology to make the determination.

(6) Malignant tumor

Producing this result generally indicates that the quality of the smear is good and that the puncturing physician is fairly confident. This is because the specificity of FNA is very high, and once “malignancy” is definitively reported, the accuracy rate is over 95%.

FNA is highly accurate and can determine the pathological staging of the tumor, especially for the most common papillary carcinoma, and for the less common medullary and undifferentiated thyroid carcinomas. However, for follicular carcinoma of the thyroid, FNA cannot differentiate benign from malignant and relies on postoperative pathology to make the final diagnosis. This is because the distinction between follicular carcinoma and benign adenoma lies in whether the envelope of the thyroid is invaded, whereas FNA can only see the cell morphology, not the envelope, and can only be clarified by postoperative paraffin pathology.

Different types of thyroid cancer are treated differently, and knowing the type of tumor preoperatively with FNA can be helpful for surgery and subsequent treatment.

In addition to the above, a new test that has been added to thyroid FNA in recent years is BRAF gene mutation, which has a long “name” – murine sarcoma filtrate. vraf murine sarcoma viral oncogene homolog B (BRAF) is one of the most important proto-oncogenes in humans, and mutations in this gene are associated with cancer development. The addition of this item will help improve the accuracy of the test. A positive BRAF mutation indicates a high likelihood of malignancy; however, the absence of a mutation does not exclude the possibility of malignancy.

What if the results show a BRAF mutation, but the puncture report says it is benign? This is a complex situation, and we recommend that you seek professional help to make a further determination, taking into account the ultrasound report and clinical palpation.

Summary

Thyroid puncture results are complex, but the summary is simple:

Benign results (2, 3): follow-up is the main focus;

Malignant/suspected malignant (4, 5, 6): surgery;

Unable to determine (1): repeat puncture.

When you get the test report, you can compare the results with several of the above to do a preliminary understanding and follow the doctor’s advice for the next step of treatment.