Thyroid biopsy is done to find out whether a thyroid nodele is cancer or not, and if cancer, what the type of cancer is. For this, fine needle aspiration biopsy (FNAB) or trucut biopsy can be used. Both are done with special needles using ultrasound guidance and local anesthesia. In FNAB, a very thin needle is inserted into the nodule and cells are aspirated into a syringe. In trucut biopsy, a cutting needle is inserted into the nodule and cylinders of tissue samples are obtained.

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In the thyroid, the standart biopsy is FNAB since it is easier to perform. However, FNAB is successful in making a confident diagnosis in about 70% of cases. In the remaining 30%, the result is either "nondiagnostic", which means that the aspirated cells are not enough, or "inconclusive", which means that the pathologist can not be sure whether the nodule is cancer or not. In such cases, a second biopsy should be done instead of operating the patient directly. Not infrequently however, the second even the third biopsies may be nondiagnostic or inconclusive, and thus, the patient has to undergo surgery. Unfortunately, upto 70% of these nodules prove to be benign (not cancer) on pathology, which means that the surgery was in fact not necessary. For this reason, many authors including us, recommend FNAB plus trucut biopsies as the second and third biopsy procedures. It has been shown that FNAB + trucut biopsy can provide a definitive diagnosis in nearly 90% of these nondiagnostic / inconclusive cases and prevent unnecessary surgeries. However in the thyroid, trucut biopsy is technically more challenging than FNAB and can be performed in only certain centers.

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Video: How is FNAB performed?

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Advantages of trucut biopsy in the thyroid

• FNAB obtain cells, which may be difficult to evaluate for the pathologist, but trucut biopsy obtains tissue pieces, which are real tissue samples.

• Trucut biopsy provides a more confident diagnosis in nondiagnostic and inconclusive cases.

• It can be done under local anesthesia in the same session with FNAB.

• If the nodule is cancer, trucut biopsy allows immunochemistry analysis which can tell us what the subtype of cancer is.

Since FNAB is easier and can be done with a very thin needle, it is preferred for the first thyroid biopsy. However, if a second or third biopsies are required due to nondiagnostic or inconclusive results of FNAB, a combined trucut biopsy plus FNAB is generally recommended. 

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Is trucut biopsy used in other organs?

Trucut (core) biopsy is the standart biopsy technique in most of our organs. It is very commonly used in the breast, liver and other soft tissues. In our center, we use trucut biopsy also in the lung, pancreas, kidney, adrenal gland, lymph nodes, bone and muscle. In the thyroid, we routinely perform FNAB + trucut biopsies when the first FNAB is nondiagnostic, inconclusive or suspicious for malignancy, or when the nodule is too hard in which case it is very difficult to do a FNAB.

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